opinion: ELKINS, PRESIDENT, UNIVERSITY OF MARYLAND v. MORENO et al.
  No. 77-154.
  Argued February 22, 1978
  Decided April 19, 1978
  Brennan, J., delivered the opinion of the Court, in which Stewart, White, Marshall, Blackmun, Powell, and Stevens, JJ., joined. Rehnquist, J., filed a dissenting opinion, in which Burger, C. J., joined, post, p. 669.
  David H. Feldman, Assistant Attorney General of Maryland, argued the cause for petitioner. With him on the briefs were Francis B. Burch, Attorney General, George A. Nilson, Deputy Attorney General, and Robert A. Zarnoch, Assistant Attorney General.
  Alfred L. Scanlan argued the cause for respondents. With him on the brief was James R. Bieke.
  A brief for the American Council on Education et al. as amici curiae urging reversal was filed by Sheldon Elliot Steinbach and by the Attorneys General of their respective States as follows: Robert F. Stephens of Kentucky, Francis X. Bellotti of Massachusetts, Anthony F. Troy of Virginia, Avrum Gross of Alaska, Carl R. Ajello of Connecticut, Richard R. Wier, Jr., of Delaware, Arthur K. Bolton of Georgia, Wayne L. Kidwell of Idaho, Theodore L. Sendak of Indiana, William J. Guste, Jr., of Louisiana, Joseph E. Brennan of Maine, A. F. Summer of Mississippi, Jphñ D. Ashcroft of Missouri, Paul L. Douglas of Nebraska, Robert List of Nevada, David H. Souter of New Hampshire, William F. Hyland of New Jersey, Toney Anaya of New Mexico, Louis J. Lefkowitz of New York, Rufus L. Edmisten of North Carolina, Allen I. Olson of North Dakota, James A. Redden of Oregon, Daniel R. McLeod of South Carolina, William Janklow of South Dakota, Robert B. Hansen of Utah, M. Jerome Diamond of Vermont, Chauncey H. Browning, Jr., of West Virginia, and V, Frank Mendicino of Wyoming.
  Mr. Justice Brennan
  delivered the opinion of the Court.
  Respondents, representing a class of nonimmigrant alien residents of Maryland, brought this action against the University of Maryland and its President, petitioner Elkins, alleging that the University’s failure to grant respondents “in-state” status for tuition purposes violated various federal laws, the Due Process and Equal Protection Clauses of the Fourteenth Amendment, and the Supremacy Clause. The District Court held for respondents on the ground that the University’s procedures for determining in-state status violated principles established in Vlandis v. Kline, 412 U. S. 441 (1973), and the Court of Appeals affirmed. Moreno v. University of Maryland, 420 F. Supp. 541 (Md. 1976), affirmance order, 556 F. 2d 573 (CA4 1977). We granted certiorari to consider whether this decision was in conflict with Weinberger v. Salfi, 422 U. S. 749 (1975). 434 U. S. 888 (1977).
  Because we find that the federal constitutional issues in this case cannot be resolved without deciding an important issue of Maryland law “as to which it appears . . . there is no controlling precedent in the Court of Appeals of [Maryland]/’ Md. Cts. & Jud. Proc. Code Ann. § 12-601 (1974), we first decide some preliminary issues of federal law and then certify the question of state law set out infra, at 668-669, to the Maryland Court of Appeals.
  I
  In 1973 the University of Maryland adopted a general policy statement with respect to “In-State Status for Admission, Tuition, and Charge-Differential Purposes.” In relevant part, this statement provides:
  “1. It is the policy of the University of Maryland to grant in-state status for admission, tuition and charge-differential purposes to United States citizens, and to immigrant aliens lawfully admitted for permanent residence in accordance with the laws of the United States, in the following cases:
  “a. Where a student is financially dependent upon a parent, parents, or spouse domiciled in Maryland for at least six consecutive months prior to the last day available for registration for the forthcoming semester.
  “b. Where a student is financially independent for at least the preceding twelve months, and provided the student has maintained his domicile in Maryland for at least six consecutive months immediately prior to the last day available for registration for the forthcoming semester.” Brief for Petitioner 7.
  The term “domicile” is defined as “a person’s permanent place of abode; namely, there must be demonstrated an intention to live permanently or indefinitely in Maryland.” Id., at 8. The policy statement also sets out eight factors to be considered in determining domicile, of which one is whether a student, or the persons on whom he is dependent, pays “Maryland income tax on all earned income including all taxable income earned outside the State.” Id., at 9.
  In addition to establishing criteria for conferring in-state status, the general policy statement establishes an administrative regime in which a person seeking in-state status initially files documentary information setting out the basis for his claim of domicile. See id., at 8-9. If the claim is denied, the person seeking in-state status may appeal, first through a personal interview with a “campus classification officer,” then to an “Intercampus Review Committee (IRC),” and finally to petitioner Elkins, as President of the University. See id., at
  In 1974, respondents Juan C. Moreno and Juan P. Otero applied for in-state status under the general policy statement. Each respondent was a student at the University of Maryland and each was dependent on a parent who held a “G-4 visa,” that is, a nonimmigrant visa granted to “officers, or employees of . . . international organizations, and the members of their immediate families” pursuant to 8 U. S. C. § 1101. (a) (15) (G) (iv) (1976 ed.). Initially, respondent Moreno was denied in-state status because “neither Mr. Manuel Moreno nor his son, Juan Carlos, are Maryland domiciliarles.” Record 41. Respondent Otero was denied in-state status because he was neither a United States citizen nor an alien admitted for permanent residence. Id., at 80.
  These respondents took a “consolidated appeal” to the IRC, which also denied them in-state status in a letter which stated:
  “The differential in tuition for in-state and out-of-state fees is based upon the principle that the State of Maryland should subsidize only those individuals who are subject to the full scope of Maryland tax liability. Such taxes support in part the University. The University of Maryland’s present classification policies rest upon this principle of cost equalization. In examining the particulars of your case it is felt that neither you nor your parents are subject to' the full range of Maryland taxes (e. g., income tax) and therefore the University must classify you as out-of-state with the consequential higher tuition rate.
  “You have raised the question of domicile. It is our opinion that a holder of a G-4 visa cannot acquire the requisite intent to reside permanently in Maryland, such intent being necessary to establish domicile.” Id., at 51, 86.
  A final appeal was made to President Elkins, who advised Moreno and Otero as follows:
  “It is the policy of the University of Maryland to grant in-state status for admission, tuition and charge-differential purposes only to United States citizens and to immigrant aliens lawfully admitted for permanent residence. Furthermore, such individuals (or their parents) must display Maryland domicile. This classification policy reflects the desire to equalize, as far as possible, the cost of education between those who support the University of Maryland through payment of the full spectrum of Maryland taxes, and those who do not. In reviewing these cases, it does not appear that the parents pay Maryland income tax. It is my opinion, therefore, that the aforesaid purpose of the policy, as well as the clear language of the policy, requires the classification of Mr. Moreno and Mr. Otero as 'out-of-state.’
  “The University’s classification policy also distinguishes between domiciliaries and non-domiciliaries of Maryland. In this regard, it is my opinion, and the position of the University, that the terms and conditions of a G-4 non-immigrant visa preclude establishing the requisite intent necessary for Maryland domicile. Thus, because Mr. Moreno and Mr. Otero are not domiciliaries of Maryland, and because of the underlying principle of cost equalization, I am denying the requests for reclassification.” App. 12A.
  Respondent Clare B. Hogg’s experience was similar. Her application for in-state status was initially rejected because:
  ''[T]he policy for the determination of in-state status limits the ability to establish an in-state classification to United States citizens and immigrant aliens admitted to the United States for permanent residence. As the person upon whom you are dependent holds a G--4 visa, and as you hold a G-4 visa, in my judgment you are not eligible for an in-state classification.
  ''Also, the person upon whom you are dependent does not pay Maryland income tax on all earned income, including income earned outside the state. I feel this further weakens your request for reclassification as this is an important criteria [sic] in determination of domicile.” Record 106.
  However, the IRC stated on appeal:
  "It is the opinion of the IRC that a holder of a non-immigrant visa, including the G-4 visa you hold, cannot acquire the requisite intent to reside permanently in Maryland, such intent being necessary to establish domicile.” Id., at 111.
  No mention was made of failure to pay taxes or of respondents’ nonimmigrant status. See ibid. Yet on final appeal to President Elkins, these reasons, as well as respondent Hogg’s lack of domicile,, were recited in a letter virtually identical to those sent respondents Moreno and Otero as grounds for denying in-state status. See App. 13A.
  Unable to obtain in-state status through the University’s administrative machinery, respondents filed a class action against the University and petitioner Elkins, seeking a declaration that the class .should be granted in-state status and seeking permanently to enjoin the University from denying in-state status to any present or future class member on the ground that such class member or a parent on whom such class member might be financially dependent
  “(a) is the holder of a G-4 visa; (b) pays no Maryland State income tax on a salary or wages from an international organization under the provisions of an international treaty to which the United States is a party; or (c) is not domiciled in the State of Maryland by reason of holding such a visa or paying no Maryland State income tax on such salary or wages under the provisions of such a treaty.” Id., at 11A.
  The District Court, on cross-motions for summary judgment, limited the relief granted to a declaration and enforcing injunction restraining petitioner Elkins from denying respondents “the opportunity to establish ‘in-state’ status” solely because of an “irrebuttable presumption of non-domicile.” 420 F. Supp., at 565. The court specifically refused to grant respondents in-state status, holding that the facts with respect to the respondents’ fathers, on whom each respondent was dependent, were in dispute. Id., at 564^565. Similarly, the court did not indicate whether the University could or could not exclude respondents because their fathers paid no Maryland state income taxes.
  With respect to the “irrebuttable presumption” issue, the District Court first held that, although each respondent had been allowed to submit a complete statement of facts supporting his or her claim of domicile to University authorities, there had been no individualized hearing because the University had a “predetermined conclusion concerning the domicile of a G-4 alien,” id., at 555, namely, that a G-4 could not have the requisite intent to establish domicile. It then ruled that aliens holding G-4 visas could as a matter of Maryland common law become Maryland domiciliarles so long as such aliens were legally capable of changing domicile as a matter of federal law. See id., at 555-556. An examination of the Immigration and Nationality Act of 1952,66 Stat. 163, as amended, 8 U. S. C. § 1101 et seq., demonstrated that G-4 aliens, as distinguished from some other classes of aliens, had the legal capacity to change domicile as a matter of federal law. See 420 F. Supp., at 556-559. Accordingly, the University’s irrebuttable presumption that G-4 aliens could not become Maryland domiciliarles was not universally true. Since “reasonable alternative means of making the crucial [domicile] determination,” Vlandis v. Kline, 412 U. S., at 452, were readily at hand, the University’s policy violated the Due Process Clause of the Fourteenth Amendment. See 420 F. Supp., at 559-560. These conclusions were affirmed by the Court of Appeals for the Fourth Circuit, which adopted the reasoning of the District Court. App. to Pet. for Cert. 54a-55a.
  Ill
  A
  In this Court, petitioner argues that the University’s instate policy should have been tested under standards set out in Weinberger v. Salfi, 422 U. S. 749 (1975), and its progeny, since in petitioner’s view these cases have effectively overruled Vlandis. As an alternative argument, petitioner asserts that the District Court should be reversed because its conclusions on points of Maryland and federal law were erroneous and in fact it is universally true that a G-4 visa holder cannot become a Maryland domiciliary.
  Respondents reply that Vlandis was distinguished, not overruled, by Salfi, and, as distinguished, Vlandis covers this case. Moreover, they assert that the District Court correctly interpreted federal and Maryland law. Because the University’s policy would on this view discriminate against a class of aliens who could become Maryland domiciliarles, they also argue, as they did in the District Court, that they should prevail on equal protection grounds even if they cannot prevail under Vlandis. Cf. Nyquist v. Mauclet, 432 U. S. 1 (1977).
  Although the parties argue this case in terms of due process, equal protection, and Vlandis versus Salfi, the gravamen of their dispute is unquestionably whether, as a matter of federal and Maryland law, G-4 aliens can form the intent necessary to allow them to become domiciliarles of Maryland. The University has consistently maintained throughout this litigation that, notwithstanding other possible interpretations of its policy statement, its “paramount” and controlling concern is with domicile as defined by the courts of Maryland. It has eschewed any interest in creating a classwide exclusion based solely on nonimmigrant status or, apparently, on the fact that many G-4 aliens receive earned income that is exempt from Maryland taxation. Because petitioner makes domicile the “paramount” policy consideration and because respondents’ contention is that they can be domiciled in Maryland but are conclusively presumed to be unable to do so, this case is squarely within Vlandis as limited by Salfi to those situations in which a State “purport[s] to be concerned with [domicile, but] at the same time den[ies] to one seeking to meet its test of [domicile] the opportunity to show factors clearly bearing on that issue.” Weinberger v. Salfi, 422 U. S., at 771.
  If we are to reverse the courts below, therefore, we must overrule or further limit Vlandis as, of course, petitioner has asked us to do. Before embarking on a review of the constitutional principles underlying Vlandis, however, proper concern for stare decisis joins with our longstanding policy of avoiding unnecessary constitutional decisions to counsel that a decision on the continuing vitality of Vlandis be avoided unless it is really necessary. See, e. g., Bellotti v. Baird, 428 U. S. 132, 146-151 (1976); Reetz v. Bozanich, 397 U. S. 82 (1970); Harman v. Forssenius, 380 U. S. 528, 534 (1965); Harrison v. NAACP, 360 U. S. 167, 177 (1959); Railroad Comm’n v. Pullman Co., 312 U. S. 496 (1941); cf. Ashwander v. TV A, 297 U. S. 288, 346-347 (1936) (Brandeis, J., concurring). So far, no such showing of necessity has been made out: If G-4 aliens cannot become domiciliaries, then respondents have no due process claim under either Vlandis or Saif, for any “irrebuttable presumption” wotild be universally true. On the other hand, the University apparently has no interest in continuing to deny in-state status to G-4 aliens as a class if they can become Maryland domiciliaries since it has indicated both here and in the District Court that it would redraft its policy “to accommodate” G-4 aliens were the Maryland courts to hold that G-4 aliens can have the requisite intent.
  Accordingly, the question whether G-4 aliens have the capacity to acquire Maryland domicile is potentially dispositive of this case. Since the resolution of this question turns on federal statutory law and Maryland common law as to each of which there are no controlling precedents, we first set out the correct meaning of federal law in this area and then sua sponte certify this case to the Court of Appeals of Maryland in order to clarify state-law aspects of the domicile question.
  B
  Petitioner has argued, and respondents do not appear to disagree, that, if as a matter of federal law a nonimmigrant alien is required to maintain a permanent residence abroad or must state that he will leave the United States at a certain future date, then such an alien’s subjective intent to reside permanently or indefinitely in a State would not create the sort of intent needed to acquire domicile. It is not clear whether this argument is based on an understanding of the common law of Maryland defining intent or whether it is based on an argument that federal law creates a “legal disability,” see Restatement (Second) of Conflict of Laws § 15 (1) (1971), which States are bound to recognize under the Supremacy Clause. See Nyquist v. Mauclet, 432 U. S., at 4; id., at 20 n. 3 (Rehnquist, J., dissenting); Seren v. Douglas, 30 Colo. App. 110, 114-115, 489 P. 2d 601, 603 (1971) (semble); Gosschalk v. Gosschalk, 48 N. J. Super. 566, 574-575, 138 A. 2d 774, 779 (semble), aff’d, 28 N. J. 73, 145 A. 2d 327 (1958); Gosschalk v. Gosschalk, 28 N. J. 73, 75-82, 145 A. 2d 327, 328-331 (1958) (dissenting opinion). But cf. Williams v. Williams, 328 F. Supp. 1380, 1383 (V. I. 1971). In any case, we need not decide the effect of a federal law restricting nonimmigrant aliens postulated above, since it is clear that Congress did not require G-4 aliens to maintain a permanent residence abroad or to pledge to leave the United States at a date certain.
  After extensive study, Congress passed the Immigration and Nationality Act of 1952, 66 Stat. 163, as amended, 8 U. S. C. § 1101 et seq. (1976 ed.), as a comprehensive and complete code covering all aspects of admission of aliens to this country,, whether for business or pleasure, or as immigrants seeking to become permanent residents. See H. R. Rep. No. 1365, 82d Cong., 2d Sess., 27 (1962); S. Rep. No-. 1137, 82d Cong., 2d Sess., 1-2 (1952). As amended in 1976, the Act establishes two immigration quotas, one for the Eastern and one for the Western Hemisphere. The object of the quotas is to limit the number of aliens who can be admitted to the United States for permanent residence. To this end, the Act divides aliens into two classes. The first class, immigrant aliens, includes every alien who does not fall into an exclusion established by § 101 (a) (15) of the Act, 66 Stat. 167, as amended, 8 U. S. C. §1101 (a)(15) (1976 ed.). Except for immigrant aliens who are “immediate relatives of United States citizens” or “special immigrants defined in section 101 (a) (27),” each alien admitted for permanent residence or who- later becomes eligible for permanent residence is chargeable against a quota and no alien can be granted permanent residence status unless a quota allocation is available. However, it is important to note that there is no requirement in the Act that an immigrant alien have an intent to- stay permanently in the United States.
  The second class of aliens, nonimmigrant aliens, is established by § 101 (a) (15) of the Act. This section creates 12 subcategories of aliens who may come to the United States without need for a quota allocation. See §§ 101 (a)(15)(A)-(L). Congress defined nonimmigrant classes to provide for the needs of international diplomacy, tourism, and commerce, each of which requires that aliens be admitted to the United States from time to time and all of which would be hampered if every alien entering the United States were subject to a quota and to the more strict entry conditions placed on immigrant ■ aliens.
  Although nonimmigrant aliens can generally be viewed as temporary visitors to the United States, the nonimmigrant classification is by no means homogeneous with respect to the terms on which a nonimmigrant enters the United States. For example, Congress expressly conditioned admission for some purposes on an intent not to abandon a foreign residence or, by implication, on an intent not to seek domicile in the United States. Thus, the 1952 Act defines a visitor to the United States as “an alien . . . having a residence in a foreign country which he has no intention of abandoning” and who is coming to the United States for business or pleasure. § 101 (a) (15) (B). Similarly, a nonimmigrant student is defined as “an alien having a residence in a foreign country which he has no intention of abandoning . . . and who seeks to enter the United States temporarily and solely for the purpose of pursuing ... a course of study . . . .” § 101 (a)(15)(F). See also § 101 (a)(15)(C) (aliens in “immediate and continuous transit”); § 101 (a) (15) (D) (vessel crewman “who intends to land temporarily”); § 101 (a)(15)(H) (temporary worker having residence in foreign country “which he has no intention of abandoning”).
  By including restrictions on intent in the definition of some nonimmigrant classes, Congress must have meant aliens to be barred from these classes if their real purpose in coming to the United States was to immigrate permanently. Moreover, since a nonimmigrant alien who does not maintain the conditions attached to his status can be deported, see § 241 (a) (9) of the 1952 Act, 66 Stat. 206, 8 U. S. C. § 1251 (a)(9) (1976 ed.), it is also clear that Congress intended that, in the absence of an adjustment of status (discussed below), nonimmigrants in restricted classes who sought to establish domicile would be deported.
  But Congress did not restrict every nonimmigrant class. In particular, no restrictions on a nonimmigrant’s intent were placed on aliens admitted under § 101 (a)(15)(G)(iv). Since the 1952 Act was intended to be a comprehensive and complete code, the conclusion is therefore inescapable that, where as with the G-4 class Congress did not impose restrictions on intent, this was deliberate. Congress’ silence is therefore pregnant, and we read it to mean that Congress, while anticipating that permanent immigration would normally occur through immigrant channels, was willing to allow nonrestricted nonimmigrant aliens to adopt the United States as their domicile. Congress’ intent is confirmed by the regulations of the Immigration and Naturalization Service, which provide that G-4 aliens are admitted for an indefinite period— so long as they are recognized by the Secretary of State to be employees or officers (or immediate family members of such employees or officers) of an international treaty organization. See 8 CFR § 214.2 (g) (1977); 1 C. Gordon & H. Rosenfield, Immigration Law and Procedure § 2.13b, p. 2-101 (rev. ed. 1977). Whether such an adoption would confer domicile in a State would, of course, be a question to be decided by the State.
  Under present law, therefore, were a G-4 alien to' develop a subjective intent to stay indefinitely in the United States, he would be able to do so without violating either the 1952 Act, the Service’s regulations, or the terms of his visa. Of course, should a G-4 alien terminate his employment with an international treaty organization, both he and his family would lose their G-4 status. Ibid. Nonetheless, such an alien would not necessarily be subject to deportation nor would he have to leave and re-enter the country in order to become an immigrant.
  Beginning with the 1952 Act, Congress created a mechanism, “adjustment of status,” through which an alien already in the United States could apply for permanent residence status. See § 245 of the 1952 Act, 66 Stat. 217, as amended, 8 U. S. C. § 1255 (1976 ed.). Prior to that time, aliens in the United States who were not immigrants had to leave the country and apply for an immigrant visa at a consulate abroad. See 2 Gordon & Rosenfield, supra, at § 7.7. Although adjustment of status is a matter of grace, not right, the most recent binding decision of the Board of Immigration Appeals states:
  “Where adverse factors are present in a given application, it may be necessary for the applicant to offset these by a showing of unusual or even outstanding equities. Generally, favorable factors such as family ties, hardship, length of residence in the United States, etc., will be considered as countervailing factors meriting favorable exercise of administrative discretion. In the absence of adverse factors, adjustment will ordinarily be granted, still as a matter of discretion.” Matter of Arai, 13 I. & N. Dec. 494, 496 (1970) (emphasis added), modifying Matter of Ortiz-Prieto, 11 I. & N. Dec. 317 (BIA 1965).
  The adverse factors referred to by the Board include such things as entering the United States under fraudulent circumstances or committing crimes while in the United States. There is no indication that any named respondent is subject to any such adverse factor, and, given each named respondent’s alleged length of residence in the United States, it would appear that any respondent could adjust his or her status to that of a permanent resident without difficulty.
  C
  For the reasons stated above, the question whether G-4 aliens can become domiciliaries of Maryland is potentially dis-positive of this case and is purely a matter of state law. Therefore, pursuant to Subtit. 6 of Tit. 12 of the Md. Cts. & Jud. Proc. Code, the following question is certified to the Court of Appeals of Maryland:
  “Are persons residing in Maryland who hold or are named in a visa under 8 U. S. C. § 1101 (a) (15) (G) (iv) (1976 ed.), or who are financially dependent upon a person holding or named in such a visa, incapable as a matter of state law of becoming domiciliaries of Maryland?”
  So ordered.
  The class certified by the District Court differs from that alleged in the complaint. As certified, the class is defined as:
  “All persons now residing in Maryland who are current students at the University of Maryland, or who chose not to apply to the University of Maryland because of the challenged policies but would now be interested in attending if given an opportunity to establish in-state status, or who are currently students in senior high schools in Maryland, and who
  “(a) hold or are named within a visa under 8 U. S. C. § 1101 (a) (15) (G) (iv) or are financially dependent upon a person holding or named within such a visa.” Moreno v. University of Maryland, 420 F. Supp. 541, 564 (Md. 1976).
  The University was dismissed from the suit on the authority of Monroe v. Pape, 365 U. S. 167 (1961). See 420 F. Supp., at 548-550.
  The complaint alleged that petitioner’s conduct violated 42 U. S. C. §§ 1981, 1983, 2000a, 2000a-1, 2000a-3, 2000d. App. 3A. Jurisdiction was predicated on 28 U. S. C. §§ 1343 (3), 1343 (4). The District Court proceeded on the premise that 42 U. S. C. § 1983 and the cited sections of Title 28 gave jurisdiction and a cause of action. See 420 F. Supp., at 548. Neither of these rulings is now in dispute.
  “(15) The term ‘immigrant’ means every alien except an alien who is within one of the following classes of nonimmigrant aliens—
  “(G) . . . (iv) officers, or employees of . . . international organizations [recognized under the International Organizations Immunities Act, 59 Stat. 669, 22 U. S. C. §288 et seql], and the members of their immediate families.”
  Respondents Moreno and Otero are dependents of employees of the Inter-American Development Bank. App. 6A, 7A. Respondent Hogg is the dependent of an employee of the International Bank for Reconstruction and Development. Id,., at 9A. The complaint states that respondent Moreno has resided in Maryland for 15 years, Otero for 10 years, and Hogg for 5 years. Id., at 4A.
  The District Court did not set out reasons for denying this relief. However, it must have believed that the University would not exclude respondents from in-state status solely for cost-equalization reasons if they otherwise qualified for Maryland domicile. If this was not the case, the District Court could not, as it did, see 420 F. Supp., at 560, have found it unnecessary to pass on respondents’ argument that the Supremacy Clause prohibits the States from penalizing those who seek to avail themselves of tax exemptions granted by federal treaties. Moreover, an examination of the pleadings before the District Court strongly suggests that, notwithstanding the correspondence set out above, the University has disavowed any intention to exclude respondents from in-state status solely because they, or the persons on whom they are dependent, paid no state income taxes. Thus, the University unequivocally denied respondents’ allegation that
  “(b) students whose parents do not pay Maryland income taxes on income earned from an international organization under the provisions of an international treaty . . . may not be granted in-state status because of the 'principle of cost equalization’ and because the University’s 'policy reflects the desire to equalize, as far as possible, the cost of education between those who support the University of Maryland through payment of the full spectrum of Maryland taxes, and those who do not’ . . . .” App. 5A (Complaint ¶ 13 (b)).
  See App. 16A (Answer ¶ 13). The University similarly disavowed any intent to exclude respondents solely on the basis of failure to pay state income taxes in its responses to respondents’ requests for admission. See Record 134 (¶2 (d)) (denying that tax exemption given some G-4 visa holders is “relevant to the determination made pursuant to the . . . University of Maryland policy”); id., at 135 (¶3 (d)) (same); id., at 139 (¶ 6 (d)) (same); id., at 136 (¶ 4 (d)) (denying the relevance for in-state tuition purposes of the fact that a person may pay Maryland state taxes on less than 50% of his earned income); id., at 141 (¶ 8 (d)) (same) ; id., at 142 (¶9 (d)) (same); id., at 140 (¶7 (d)) (denying the relevance for in-state tuition purposes of the fact that a person may pay Maryland state taxes on only .“unearned” income). Finally, the University admitted as fact that
  “an 'immigrant student’ who is financially dependent upon a parent who is an immigrant lawfully admitted for permanent residence . . . may be granted in-state status, whether or not the parent on whom such student is financially dependent currently pays Maryland income tax, provided that such parent can exhibit all of the other relevant domiciliary criteria . . . .” Id., at 142.
  Since no party has suggested a difference between immigrant and nonimmigrant aliens other than the possibility that the latter cannot become domiciliarles, the University’s admission tends to confirm that the tax issue is not determinative of in-state status for any group of aliens.
  For the reasons set out above, we, like the District Court, do not now decide whether the University would be barred by the Supremacy Clause from denying in-state status on tax grounds.
  The District Court did not pass on the equal protection argument. See 420 F. Supp., at 560.
  The respondents also argue that the University’s policy is invalid under the Supremacy Clause since control over aliens and over foreign relations is vested exclusively in the Federal Government. We have no need to reach this argument at this time.
  Petitioner will be surprised to learn from the dissent, see post, at 672-676, that the University’s treatment of respondents is not really determined by the Maryland common law of domicile and therefore that this case is governed by Weinberger v. Salfi, 422 U. S. 749 (1975), not Vlandis v. Kline, 412 U. S. 441 (1973). For petitioner’s view of the University’s policy, contrary to that suggested by the dissent, has consistently been: “The Defendant 'University distinguishes between domiciliaries and non-domiciliaries of the State of Maryland .... This represents a policy decision of the Board of Regents of the University, which has been implemented in the rules and guidelines of the Policy Statement . . . .” Record 215 (emphasis added). And again: “The wording of the ‘In-State’ policy is structured so as to initially deny ‘in-state,’ status to non-immigrant aliens. This structure incorporates the determination that under the law and definition of domicile as established and applied by Maryland courts, non-immigrant aliens cannot display the intent to permanently reside within the State which is requisite to establishing Maryland domicile.” Id., at 217 (emphasis added). And again: “[The University’s] actions and policy rest upon a definition, not a presumption. Defendants have denied Plaintiffs ‘in-state’ status based on an evaluation of their domicile under Maryland law: the existence of a G-4 visa is merely a single operative fact, albeit paramount, which is placed in the context of what Defendants have determined to be the definition of domicile established by the Maryland courts.” Id., at 231 (second emphasis added). And again: “This distinction [between immigrant and nonimmigrant aliens] was based upon a reading of the Maryland law of domicile in conjunction with the terms and conditions of the non-immigrant visas described in 28 [sic] U. S. C. § 1101 (a) (15) (A) through (L), a determination thereby having been made that non-immigrants do not have the intent requisite for establishing Maryland domicile. . . . That State University’s [sic] can establish such . . . ‘domicile’ policies and make distinctions between domiciliaries and non-domiciliaries is well established . . . .” Id., at 233.
  Indeed, respondents argued below against abstention, see n,. 15, infra, on the same grounds now argued by our Brother Rehnquist against certification, namely: “[T]he Maryland common law of domicile is not at issue in this case. No ‘clarification’ of the Maryland common law of domicile is needed. Such common law principles, standing alone, do not set the tuition charged by the University of Maryland.” Record 272. And petitioner countered: “What [respondents] apparently fail to understand is that the [University’s] Tn-State Policy’ is structured upon and reflects [the University’s] understanding of the Maryland common law of domicile.” Id., at 340.
  There can be no doubt that, notwithstanding the policy statement’s express reservation of in-state status to United States citizens and immigrant aliens, see supra, at 651, the University has no policy of excluding nonimmigrant aliens simply because they lack immigrant status under federal law. Petitioner’s answer unequivocally states that the University has not “denied” nor does it “continu[e] to deny in-state status to all students who neither are United States citizens nor hold immigrant visas,” App. 16A, although such an across-the-board denial would be required by the University’s policy if it placed independent significance on immigrant status. Moreover, petitioner tells us that “the fact of alienage is completely irrelevant in itself to the issues controlling a determination of domicile.” Record 232.
  See n. 5, supra. Indeed, although the dissent suggests that petitioner might bar respondents on cost-equalization grounds, see post, at 672-673, it is clear that petitioner has not done this although nothing in the District Court’s injunction prohibits petitioner from doing so. See supra, at 655-656, and n. 5.
  In fact, the University allows evidence to be submitted bearing on respondents’ claims of domicile — -it simply does not evaluate that evidence.
  Moreover, respondents’ eqhal protection claim turns on whether it is in fact true that G-4 aliens can become domiciliaries of Maryland, If they cannot, the constitutional issues that would be raised are materially different from those briefed tit argued here. For this reason, we also think certification proper. See, e. g., Bellotti v. Baird, 428 U. S. 132, 146-151 (1976).
  “The core of Plaintiffs’ catise of action is their belief that under Maryland law a G-4 non-immigfant alien can be domiciled in this State. A judicial determination in the negative would foreclose their Constitutional and statutory arguments; tt determination in the affirmative would require the University’s Board of Regents to rewrite the In-State policy to accommodate this category of domiciliaries.” Record 239-240 (emphasis added).
  Similar sentiments are expressed in petitioner’s brief in this Court. See Brief, at 11, 12, 28, 30, 34, and 35 n. 20. And petitioner’s counsel stated at oral argument that If the Court of Appeals of Maryland determined that a person with a G-4 visa is capable of forming the requisite intent to establish domicile, “the odds are reasonably high that the case would become moot because the university would change its policy, but that judgment is one that would be made by the regents . . . Tr. of Oral Arg. 14 — 15.
  No recent Maryland case has been cited in the briefs either here or below. In addition, petitioner’s counsel, an Assistant Attorney General of Maryland, stated at oral argument that there “are no Maryland decisions one way or the other.” Id., at 10.
  Although petitioner asked the District Court to abstain, Record 211, he did not ask that court to certify the state-law question of domicile to the Maryland Court of Appeals. We need not decide whether the District Court’s failure to abstain was erroneous, for, as we noted in Bellotti v. Baird, supra, at 150-151:
  “This Court often has remarked that the equitable practice of abstention is limited by considerations of ‘ “the delay and expense to which application of the abstention doctrine inevitably gives rise.” ’ .. . As we have also noted, however, the availability of an adequate certification procedure 'does, of course, in the long run save time, energy, and resources and helps build a cooperative judicial federalism.’ . . .
  “. . . [T]he availability of certification greatly simplifies [Pullman abstention] analysis.” (Footnotes omitted.)
  Although it is our frequent practice to defer to a construction of state law made by a district court and affirmed by a court of appeals whose jurisdiction includes the State whose law is construed, see, e. g., Bishop v. Wood, 426 U. S. 341, 345-346, and 346-347, n. 10 (1976) (collecting cases), we do not do so here for two reasons. First, the question of who can become a domiciliary of a State is one in which state governments have the highest interest. Many issues of state law may turn on the definition of domicile: for example, who may vote; who may hold public office; who may obtain a divorce; who must pay the full spectrum of state taxes. In short, the definition of domicile determines who is a full-fledged member of the polity of a State, subject to the full power of its laws and participating (except, of course, with respect to aliens) fully in its governance. Second, the status of the many foreign nationals living in Maryland is of great importance to Maryland because it potentially affects Maryland's relations with the Federal Government, other state and local governments in the greater District of Columbia area, and foreign nations. In a federal system, it is obviously desirable that questions of law which, like domicile, are both intensely local and immensely important to a wide spectrum of state government activities be decided in the first instance by state courts. This may not always be possible nor is it always required, but where as here there is an efficient method for obtaining a ruling from the highest court of a State we do not hesitate to avail ourselves of it. In so doing, we emphasize that we do not in any way suggest that the District Court's determination of Maryland law was incorrect.
  Immigration and. Nationality Act Amendments o-f 1976, § 2, 90 Stat. 2703, amending § 201 of the 1952 Act, as amended, 8 U. S. C. § 1151 (1976 ed.).
  § 201 of the 1952 Act, as amended, 8 U. S. C. § 1151 (1976 ed.).
  8U.S.C. § 1151 (1976 ed.).
  See S. Rep. No. 1137, 82d Cong., 2d Sess., pt. 1, p. 13 (1952); H. R. Rep. No. 1365, 82d Cong., 2d Sess., 52 (1952); H. R. Rep. No. 91-851, pp. 5-7 (1970).
  See n. 4, supra.
  Until the Immigration and Nationality Act Amendments of 1976, n. 17, supra, nonimmigrant aliens whose country of origin was in the Western Hemisphere were excluded from adjustment of status. Section 6 of the 1976 Amendments, 90 Stat. 2705, removed this restriction. See 8 U. S. C. §1255 (1976 ed.).
  Opinions of the Attorney General, the Board of Immigration Appeals, and of Immigration and Naturalization Service officers published in Administrative Decisions Under Immigration and Nationality Laws of the United States are “binding on all officers and employees of the Service in the administration of the [1952] Act.” 8 CFR §§3.1 (g), 103.3 (e), and 103.9 (a) (1977).
  See, e. g., Matter of Rubio-Vargas, 11 I. & N. Dec. 167 (BIA 1965); Matter of Vega, 11 I. & N. Dec. 337 (BIA 1965); Matter of Diaz-Villamil, 10 I. & N. Dec. 494 (BIA 1964); Ameeriar v. INS, 438 F. 2d 1028 (CA3), cert. dismissed, 404 U. S. 801 (1971). See also Matter of Barrios, 101. & N. Dec. 172 (BIA 1963); Brownell v. Carija, 102 U. S. App. D. C. 379, 254 F. 2d 78 (1957); Brownell v. Gutnayer, 94 U. S. App. D. C. 90, 212 F. 2d 462 (1954).
  See, e. g., Matter of Marchena, 12 I. & N. Dec. 355 (Regional Comm’r 1967); Matter of F — , 8 I. & N. Dec. 65 (Asst. Comm’r 1958). See generally Annot., 4 ALR Fed. 557 (1970).
  See n. 4, supra.
  Cf. Matter of Penaherrera, 13 I. & N. Dec. 334 (Dist. Director 1969). Although this is a class action, see n. 1, supra, there is no reason on the present record to believe that G-4 aliens as a class are less qualified for adjustment of status than are the class representatives.
  "§ 12-601. Jurisdiction granted to Court of Appeals.
  “The Court of Appeals may answer questions of law certified to it by the Supreme Court of the United States . . . when requested by the certifying court if there is involved in any proceeding before the certifying court a question of law of this state which may be determinative of the cause then pending in the certifying court and as to which it appears to the certifying court there is no controlling precedent in the Court of Appeals of this state.”
  “§ 12-602. Invocation of subtitle.
  “This subtitle may be invoked by an order of any court referred to in § 12-601 upon the court’s own motion or upon the motion of any party to the cause.”
  “§ 12-603. Certification order.
  “(a) Form. — A certification order shall set forth:
  “(1) The question, of law to be answered; and
  “(2) A statement of all facts relevant to the question certified showing fully the nature of the controversy in which the question arose.”
  The majority rule appears to be that within a single State “the rules of domicil are the same for all purposes.” Restatement (Second) of Conflict of Laws, § 11, Comment o, p. 47 (1971). Should Maryland not follow this rule, we presume that the Court of Appeals will direct its attention to domicile for the purposes of this case.
  [Reporter’s Note: Subsequently, the Maryland Court of Appeals answered the certified question, and a supplemental decision was rendered in Toll v. Moreno, 441 U. S. 458 (1979).]
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