opinion: Mr. Chief Justice Burger
  delivered the opinion of the Court.
  We granted the writ in this case to consider whether the respondent, presently confined in California under a state conviction, may utilize the federal courts in California to test the validity of a North Carolina sentence before beginning to serve that sentence and while under a detainer filed by North Carolina. Respondent claims the sentence yet to be served in North Carolina is “consecutive” under Peyton v. Rowe, 391 U. S. 54 (1968). However, since his petition challenges the present effect being given the North Carolina detainer by the California authorities, particularly with respect to granting him parole, we have concluded that as to that claim respondent failed to exhaust his state remedies and accordingly do not reach the question for which the writ was granted.
  The record discloses that on April 27, 1964, John Edward George was convicted on a plea of guilty in a California court of first-degree robbery. He began serving his sentence of five years to life at San Quentin. Following his conviction, detainers were filed in California by the States of Kansas, Nevada, and North Carolina, on June 4, 10, and 11, 1964, respectively.
  Exercising his right under Article III (a) of the interstate “Agreement on Detainers,” George requested temporary release to stand trial on the underlying robbery charge pending in North Carolina. Accordingly, on July 20, 1966, he was released to North Carolina authorities and transported there to stand trial. The North Carolina trial was held, and on February 8, 1967, George was convicted and sentenced to imprisonment for 12 to 15 years. The conviction was thereafter affirmed, State v. George, 271 N. C. 438, 156 S. E. 2d 845 (1967).
  Following the North Carolina trial George was returned to San Quentin to complete service of his California sentence. On April 14, 1967, the clerk of the Gaston County Superior Court addressed a letter to the Records Officer at San Quentin advising that George was “wanted at the termination of his imprisonment there for return to this jurisdiction to serve the sentence imposed in the Superior Court of Gaston County, North Carolina.” The Warden of San Quentin acknowledged the detainer, indicating that it was “noted in our records.”
  George then brought a petition for habeas corpus in the United States District Court for the Northern District of California in which he sought to attack not his California conviction, for which he was then incarcerated, but the North Carolina conviction for which the detainer had been filed. The District Court denied the application by order dated March 1, 1968, on the ground that McNally v. Hill, 293 U. S. 131 (1934), foreclosed habeas corpus relief on the North Carolina conviction while George was still in custody under the prior California judgment.
  George filed a petition for rehearing in the District Court in which he argued that even though he was actually serving time in a California jail and thus not technically serving his North Carolina sentence, habeas corpus was not foreclosed since the North Carolina detainer operated as a form of constructive custody. In support of his contention he drew upon the language in Arketa v. Wilson, 373 F. 2d 582 (C. A. 9th Cir. 1967), to the effect that the strict rule of McNally v. Hill had been somewhat eroded by this Court’s subsequent decisions in Ex parte Hull, 312 U. S. 546 (1941), and Jones v. Cunningham, 371 U. S. 236 (1963), and that “it appears that there are situations in which the writ can be used to free a petitioner from a certain type of custody, rather than from all custody.” Arketa v. Wilson, supra, at 584. George argued that the North Carolina warrant was “a form of custody” since it affected his custodial classification and probability of parole on his California sentence. On March 20, 1968, the District Court denied the petition for rehearing and George appealed to the Court of Appeals for the Ninth Circuit.
  Our decision in Peyton v. Rowe intervened. In that case we overruled McNally v. Hill, 293 U. S. 131 (1934), and held that a state prisoner serving consecutive sentences in the forum state is “in custody” under each sentence for purposes of jurisdiction for collateral attack under 28 U. S. C. § 2241 (c)(3), thus permitting a federal habeas corpus action to test a future state sentence while he is serving an earlier sentence. In Peyton v. Rowe the consecutive sentences were imposed by the forum State, and the sentences were being served in that State’s prison. Unlike the case now before us, in such a single-state situation the challenge to the continuing vitality of Ahrens v. Clark, 335 U. S. 188 (1948), does not arise. See Word v. North Carolina, 406 F. 2d 352 (C. A. 4th Cir. 1969).
  As we have noted, having named the Warden of San Quentin as the respondent in his amended petition to the Federal District Court in California and having had his petition refused, George sought rehearing. In that application George alleged that the California authorities had imposed upon him a “form of custody” because of the North Carolina detainer. Specifically, he alleged that the mere presence of the detainer adversely affected the probability of his securing parole and the degree of security in which he was detained by state authorities. California denies that the existence of the detainer has any consequences affecting his parole potential or custodial status.
  Since the Full Faith and Credit Clause does not require that sister States enforce a foreign penal judgment, Huntington v. AttrilL, 146 U. S. 657 (1892); cf. Milwaukee County v. M. E. White Co., 296 U. S. 268, 279 (1935), California is free to consider what effect, if any, it will give to the North Carolina detainer in terms of George’s present “custody.” Because the petition for rehearing raised precisely such a challenge to the California “custody,” a matter that has not yet been presented to the California courts, we conclude that respondent George has not yet exhausted his California remedies. See Ex parte Royall, 117 U. S. 241 (1886).
  Respondent insists that the very presence of the North Carolina detainer has and will continue to have an adverse impact on California’s consideration of his claim for parole. Therefore, the United States District Court in California should retain jurisdiction of the petition for habeas corpus relief pending respondent’s further application to the California courts for whatever relief, if any, may be available and appropriate if he establishes his claim that North Carolina’s detainer interferes with relief that might, in the absence of the detainer, be granted by California. We affirm the judgment of the Court of Appeals to the extent it finds jurisdiction in the District Court to consider respondent’s claims with respect to the impact of the detainer if respondent elects to press those claims after he exhausts his remedies in the California courts.
  Affirmed.
  Mr. Justice Blackmun took no part in the consideration or decision of this case.
  Under California law the sentence for first-degree robbery is an indeterminate five years to life sentence in the discretion of the California Adult Authority. Cal. Pen. Code § 213.
  Cal. Pen. Code § 1389 (Supp. 1968).
  App. 26.
  “§ 2241. Power to grant writ.
  “(a) Writs of habeas corpus may be granted by the Supreme Court, any justice thereof, the district courts and any circuit judge within their respective jurisdictions. The order of a circuit judge shall be entered in the records of the district court of the district wherein the restraint complained of is had.
  “(e) The writ of habeas corpus shall not extend to a prisoner unless—
  “(3) He is in custody in violation of the Constitution or laws or treaties of the United States . . .
  In that case Chief Judge Haynsworth, expressing the views of the majority of the Court of Appeals for the Fourth Circuit sitting en banc, concluded that Ahrens v. Clark was a venue decision, and that the physical presence of the petitioner within the district was not an invariable requirement if rigid adherence to the rule would leave one in prison without an effective remedy. .The legislative history of the 1966 amendments to 28 U. S. C. § 2241 (d) (1964 ed., Supp. V) suggests that Congress may have intended to endorse and preserve the territorial rule of Ahrens to the extent that it was not altered by those amendments. See H. R. Rep. No. 1894, 89th Cong., 2d Sess., 1-2 (1966). See also S. Rep. No. 1502, 89th Cong., 2d Sess. (1966). Those changes were made by Congress, of course, prior to our decision in Peyton v. Rome; necessarily Congress could not have had the multistate problem with which we are now confronted in mind. Whether, in light of the legislative history of § 2241 (d) and the changed circumstances brought about by Peyton v. Rowe, the rigor of our Ahrens holding may be reconsidered is an issue upon which we reserve judgment.
  However, we note that prisoners under sentence of a federal court are confronted with no such dilemma since they may bring a challenge at any time in the sentencing court irrespective of where they may be incarcerated. 28 U. S. C. § 2255, It is anomalous that the federal statutory scheme does not contemplate affording state prisoners that remedy. The obvious, logical, and practical solution is an amendment to § 2241 to remedy the shortcoming that has become apparent following the holding in Peyton v. Rowe. Sound judicial administration calls for such an amendment.
  We are not here concerned with the scope of California’s ultimate duty, imposed by Art. IV, § 2, cl. 2, of the Constitution, to extradite persons wanted for trial or execution of sentence in a sister State. We note only that, until the obligation to extradite matures, the Full Faith and Credit Clause does not require California to enforce the North Carolina penal judgment in any way.
instruction: What follows is an opinion from the Supreme Court of the United States. Your task is to determine the ideological "direction" of the decision ("liberal", "conservative", or "unspecifiable"). Use "unspecifiable" if the issue does not lend itself to a liberal or conservative description (e.g., a boundary dispute between two states, real property, wills and estates), or because no convention exists as to which is the liberal side and which is the conservative side (e.g., the legislative veto). Specification of the ideological direction comports with conventional usage. In the context of issues pertaining to criminal procedure, civil rights, First Amendment, due process, privacy, and attorneys, consider liberal to be pro-person accused or convicted of crime, or denied a jury trial, pro-civil liberties or civil rights claimant, especially those exercising less protected civil rights (e.g., homosexuality), pro-child or juvenile, pro-indigent pro-Indian, pro-affirmative action, pro-neutrality in establishment clause cases, pro-female in abortion, pro-underdog, anti-slavery, incorporation of foreign territories anti-government in the context of due process, except for takings clause cases where a pro-government, anti-owner vote is considered liberal except in criminal forfeiture cases or those where the taking is pro-business violation of due process by exercising jurisdiction over nonresident, pro-attorney or governmental official in non-liability cases, pro-accountability and/or anti-corruption in campaign spending pro-privacy vis-a-vis the 1st Amendment where the privacy invaded is that of mental incompetents, pro-disclosure in Freedom of Information Act issues except for employment and student records. In the context of issues pertaining to unions and economic activity, consider liberal to be pro-union except in union antitrust where liberal = pro-competition, pro-government, anti-business anti-employer, pro-competition, pro-injured person, pro-indigent, pro-small business vis-a-vis large business pro-state/anti-business in state tax cases, pro-debtor, pro-bankrupt, pro-Indian, pro-environmental protection, pro-economic underdog pro-consumer, pro-accountability in governmental corruption, pro-original grantee, purchaser, or occupant in state and territorial land claims anti-union member or employee vis-a-vis union, anti-union in union antitrust, anti-union in union or closed shop, pro-trial in arbitration. In the context of issues pertaining to judicial power, consider liberal to be pro-exercise of judicial power, pro-judicial "activism", pro-judicial review of administrative action. In the context of issues pertaining to federalism, consider liberal to be pro-federal power, pro-executive power in executive/congressional disputes, anti-state. In the context of issues pertaining to federal taxation, consider liberal to be pro-United States and conservative pro-taxpayer. In miscellaneous, consider conservative the incorporation of foreign territories and executive authority vis-a-vis congress or the states or judcial authority vis-a-vis state or federal legislative authority, and consider liberal legislative veto. In interstate relations and private law issues, consider unspecifiable in all cases.