opinion: Mr. Justice Clark
  delivered the opinion of the Court.
  The petitioner, an alien, has been ordered deported to Canada as one who upon entry into this country was a homosexual and therefore “afflicted with psychopathic personality” and excludable under § 212 (a) (4) of the Immigration and Nationality Act of 1952, 66 Stat. 182, 8 U. S. C. § 1182 (a)(4). Petitioner's appeal from the finding of the Special Inquiry Officer was dismissed by the Board of Immigration Appeals, without opinion, and his petition for review in the Court of Appeals was dismissed, with one judge dissenting. 363 F. 2d 488. It held that the term “psychopathic personality,” as used by the Congress in §212 (a)(4), was a term of art intended to exclude homosexuals from entry into the United States. It further found that the term was not void for vagueness and was, therefore, not repugnant to the Fifth Amendment’s Due Process Clause. We granted certiorari, 385 U. S. 927, and now affirm.
  I.
  Petitioner, a Canadian national, was first admitted to this country on June 22, 1955, at the age of 21. His last entry was in 1959, at which time he was returning from a short trip to Canada. His mother and stepfather and three of his brothers and sisters live in the United States. In 1963 he applied for citizenship and submitted to the Naturalization Examiner an affidavit in which he admitted that he was arrested in New York in October 1959, on a charge of sodomy, which was later reduced to simple assault and thereafter dismissed on default of the complainant. In 1964, petitioner, at the request of the Government, submitted another affidavit which revealed the full history of his sexual deviate behavior. It stated that his first homosexual experience occurred when he was 14 years of age, some seven years before his entry into the United States. Petitioner was evidently a passive participant in this encounter. His next episode was at age 16 and occurred in a public park in Halifax, Nova Scotia. Petitioner was the active participant in this affair. During the next five years immediately preceding his first entry into the United States petitioner had homosexual relations on an average of three or four times a year. He also stated that prior to his entry he had engaged in heterosexual relations on three or four occasions. During the eight and one-half years immediately subsequent to his entry, and up to the time of his second statement, petitioner continued to have homosexual relations on an average of three or four times a year. Since 1959 petitioner had shared an apartment with a man with whom he had had homosexual relations.
  The 1964 affidavit was submitted to the Public Health Service for its opinion as to whether petitioner was ex-cludable for any reason at the time of his entry. The Public Health Service issued a certificate in 1964 stating that in the opinion of the subscribing physicians petitioner “was afflicted with a class A condition, namely, psychopathic personality, sexual deviate” at the time of his admission. Deportation proceedings were then instituted. ‘‘No serious question,” the Special Inquiry Officer found, “has been raised either by the respondent [petitioner here], his counsel or the psychiatrists [employed by petitioner] who have submitted reports on the respondent as to his sexual deviation.” Indeed, the officer found that both of petitioner’s psychiatrists “concede that the respondent has been a homosexual for a number of years but conclude that by reason of such sexual deviation, the respondent is not a psychopathic personality.” Finding against petitioner on the facts, the issue before the officer was reduced to the purely legal question of whether the term “psychopathic personality” included homosexuals and if it suffered illegality because of vagueness.
  II.
  The legislative history of the Act indicates beyond a shadow of a doubt that the Congress intended the phrase “psychopathic personality” to include homosexuals such as petitioner.
  Prior to the 1952 Act the immigration law excluded “persons of constitutional psychopathic inferiority.” 39 Stat. 875, as amended, 8 U. S. C. § 136 (a) (1946 ed.). Beginning in 1950, a subcommittee of the Senate Committee on the Judiciary conducted a comprehensive study of the immigration laws and in its report found “that the purpose of the provision against ‘persons with constitutional psychopathic inferiority’ will be more adequately served by changing that term to ‘persons afflicted with psychopathic personality,’ and that the classes of mentally defectives should be enlarged to include homosexuals and other sex perverts.” S. Rep. No. 1515, 81st Cong., 2d Sess., p. 345. The resulting legislation was first introduced as S. 3455 and used the new phrase “psychopathic personality.” The bill, however, contained an additional clause providing for the exclusion of aliens “who are homosexuals or sex perverts.” As the legislation progressed (now S. 2550 in the 82d Congress), however, it omitted the latter clause “who are homosexuals or sex perverts” and used only the phrase “psychopathic personality.” The omission is explained by the Judiciary Committee Report on the bill:
  “The provisio[n] of S. 716 [one of the earlier bills not enacted] which specifically excluded homosexuals and sex perverts as a separate excludable class does not appear in the instant bill. The Public Health Service has advised that the provision for the exclusion of aliens afflicted with psychopathic personality or a mental defect which appears in the instant bill is sufficiently broad to provide for the exclusion of homosexuals and sex perverts. This change of nomenclature is not to he construed in any way as modifying the intent to exclude all aliens who are sexual deviates.” (Emphasis supplied.) S. Rep. No. 1137, 82d Cong., 2d Sess., p. 9.
  Likewise, a House bill, H. R. 5678, adopted the position of the Public Health Service that the phrase “psychopathic personality” excluded from entry homosexuals and sex perverts. The report that accompanied the bill shows cléarly that the House Judiciary Committee adopted the recommendation of the Public Health Service that “psychopathic personality” should be used in the Act as a phrase that would exclude from admission homosexuals and sex perverts. H. R. Rep. No. 1365, 82d Cong., 2d Sess. It quoted at length, and specifically adopted, the Public Health Service report which recommended that the term “psychopathic personality” be used to “specify such types of pathologic behavior as homosexuality or sexual perversion.” We, therefore, conclude that the Congress used the phrase “psychopathic personality” not in the clinical sense, but to effectuate its purpose to exclude from entry all homosexuals and other sex perverts.
  Petitioner stresses that only persons afflicted with psychopathic personality are excludable. This, he says, is “a condition, physical or psychiatric, which may be manifested in different ways, including sexual behavior.” Petitioner’s contention must fall by his own admissions. For over six years prior to his entry petitioner admittedly followed a continued course of homosexual conduct. The Public Health Service doctors found and certified that at the time of his entry petitioner “was afflicted with a class A condition, namely, psychopathic personality, sexual deviate . . . .” It was stipulated that if these doctors were to appear in the case they would testify to this effect and that “no useful purpose would be served by submitting this additional psychiatric material [furnished by petitioner’s doctors] to the United States Public Health Service . . . .” The Government clearly established that petitioner was a homosexual at entry. Having substantial support in the record, we do not now disturb that finding, especially since petitioner admitted being a homosexual at the time of his entry. The existence of this condition over a continuous and uninterrupted period prior to and at the time of petitioner’s entry clearly supports the ultimate finding upon which the order of deportation was based.
  III.
  Petitioner says, even so, the section as construed is constitutionally defective because it did not adequately warn him that his sexual affliction at the time of entry could lead to his deportation. It is true that this Court has held the “void for vagueness” doctrine applicable to civil as well as criminal actions. See Small Co. v. Am. Sugar Ref. Co., 267 U. S. 233, 239 (1925). However, this is where “the exaction of obedience to a rule or standard . . . was so vague and indefinite as really to be no rule or standard at all. . . .” In short, the exaction must strip a participant of his rights to come within the principle of the cases. But the “exaction” of § 212 (a) (4) never applied to petitioner’s conduct after entry. The section imposes neither regulation of nor sanction for conduct. In this situation, therefore, no necessity exists for guidance so that one may avoid the applicability of the law. The petitioner is not being deported for conduct engaged in after his entry into the United States, but rather for characteristics he possessed at the time of his entry. Here, when petitioner first presented himself at our border for entrance, he was already afflicted with homosexuality. The pattern was cut, and under it he was not admissible.
  The constitutional requirement of fair warning has no applicability to standards such as are laid down in § 212 (a) (4) for admission of aliens to the United States. It has long been held that the Congress has plenary power to make rules for the admission of aliens and to exclude those who possess those characteristics which Congress has forbidden. See The Chinese Exclusion Case, 130 U. S. 581 (1889). Here Congress commanded that homosexuals not be allowed to enter. The petitioner was found to have that characteristic and was ordered deported. The basis of the deportation order was his affliction for a long period of time prior to entry, i. e., six and one-half years before his entry. It may be, as some claim, that “psychopathic personality” is a medically ambiguous term, including several separate and distinct afflictions. Noyes, Modern Clinical Psychiatry 410 (3d ed. 1948). But the test here is what the Congress intended, not what differing psychiatrists may think. It was not laying down a clinical test, but an exclusionary standard which it declared to be inclusive of those having homosexual and perverted characteristics. It can hardly be disputed that the legislative history of § 212 (a)(4) clearly shows that Congress so intended.
  But petitioner says that he had no warning and that no interpretation of the section had come down at the time of his 1955 entry. Therefore, he argues, he was unaware of the fact that homosexual conduct engaged in after entry could lead to his deportation. We do not believe that petitioner’s post-entry conduct is the basis for his deportation order. At the time of his first entry he had continuously been afflicted with homosexuality for over six years. To us the statute is clear. It fixes “the time of entry” as the crucial date and the record shows that the findings of the Public Health Service doctors and the Special Inquiry Officer all were based on that date. We find no indication that the post-entry evidence was of any consequence in the ultimate decision of the doctors, the hearing officer or the court. Indeed, the proof was uncontradicted as to petitioner’s characteristic at the time of entry and this brought him within the excludable class. A standard applicable solely to time of entry could hardly be vague as to post-entry conduct.
  The petitioner raises other points, including the claim that an “arriving alien” under the Act is entitled to medical examination. Since he is not. an “arriving alien” subject to exclusion, but a deportable alien within an ex-cludable class — who through error was permitted entry— it is doubtful if the requirement would apply. But we need not go into the question since petitioner was twice offered examination and refused to submit himself. He can hardly be heard to complain now. The remaining contentions are likewise without merit.
  Affirmed.
  “Sec. 212. (a) Except as otherwise provided in this Act, the following classes of aliens shall be ineligible to receive visas and shall be excluded from admission into the United States:
  “(4) Aliens afflicted with psychopathic personality, epilepsy, or a mental defect . . . .”
  Section 241(a)(1) of the Immigration and Nationality Act, 66 Stat. 204, 8 U. S. C. § 1251 (a)(1), provides that: “Any alien in the United States . . . shall, upon the order of the Attorney General, be deported who — (1) at the time of entry was within one or more of the classes of aliens excludable by the law existing at the time of such entry . . . .”
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