opinion: Mr. Chief Justice Vinson
  delivered the opinion of the Court.
  This case originated on October 21, 1950, when petitioner, a prisoner in San Quentin, filed an application for a writ of habeas corpus in the Supreme Court of California. That court, summarily, but with two dissents, denied the application. To review this decision, petitioner applied to this Court for certiorari. The Court granted the petition, 341 U. S. 938, and thereafter appointed counsel to represent the petitioner. 342 U. S. 805.
  The Attorney General of California appeared for respondent. At the bar of this Court, he argued that the judgment of the Supreme Court of California rested on an adequate nonfederal ground. Admitting that habeas corpus is ordinarily an available means to California prisoners to challenge the constitutionality of the proceedings which resulted in their incarceration, the Attorney General told us that the writ was unavailable in this particular case, to this particular petitioner because he could have and should have presented his federal claim in an appeal from his original conviction. Counsel for petitioner vigorously opposed this contention, insisting that habeas corpus was an available remedy under California law, that the federal question was properly before the court.
  This Court, of course, does not sit to determine matters of state law; nor is it the appropriate forum to resolve the argument raised by the earnest objections of the Attorney General of California.
  Accordingly, we followed our precedents. We continued the cause “for such period” as would “enable counsel for petitioner to secure a determination from the Supreme Court of California as to whether the judgment herein was intended to rest on an adequate independent state ground or whether decision of the federal claim was necessary to the judgment rendered.” 342 U. S. 33, 34. (Emphasis supplied.)
  Counsel for petitioner, in December 1951, duly filed in the Supreme Court of California a “Petition for Determination of Basis of Judgment” which requested an expression by that court on the issue raised by our order. Subsequently, the Clerk of this Court received a letter from the Clerk of the Supreme Court of California relative to this question. But we received no official determination of the issue from the Supreme Court of California.
  We could not regard the letter from the Clerk of the Supreme Court of California as a “sufficient ‘determination’ of the question raised in our order of November 5, 1951.” Therefore, on May 12, 1952, we “further continued” the cause on our docket to enable counsel for petitioner to secure from the Supreme Court of California its official determination as requested by our earlier order. 343 U. S. 393.
  Though some months have now elapsed, we still have received no advice from the Supreme Court of California. We are informed, however, that the California court advised petitioner’s counsel informally that it doubted its jurisdiction to render such a determination. And, although counsel subsequently submitted briefs to the contrary, the California court again informed counsel, through its Clerk, that it was powerless, for want of jurisdiction, to issue any further official expression on the case. It appears, then, that so long as this cause continues on our docket, counsel cannot procure that which we asked him to procure.
  We granted certiorari in this case “because of a serious claim that petitioner had been deprived of his rights under the Federal Constitution.” 342 U. S. 33. This Court, alone, is the final arbiter of such a claim, and our grant of certiorari should entitle petitioner to the chance to have the matter resolved by this Court — provided that the state judgment was not based on an adequate state ground. If the state judgment was based on an adequate state ground, the Court, of course, would be without jurisdiction to pass upon the federal question. Doubt has since arisen that such, jurisdiction exists. These circumstances should not now act to deprive petitioner of his day in this Court, but they do require that we take scrupulous care, as we have so often done before, to determine our jurisdiction. This involves further delay, and in this case further delay is regrettable. But delay is necessary unless we are to resolve the jurisdictional issue by simply assuming the nonexistence of an adequate state ground though in fact one may exist.
  To the end that the doubt in this case may be resolved, we vacate the judgment of the Supreme Court of California and remand the cause for further proceedings. A new judgment may be entered, and petitioner also may be informed by an official determination from the Supreme Court of California whether or not that judgment rests on an adequate state ground.
  So ordered.
  Loftus v. Illinois, 334 U. S. 804 (1948); Herb v. Pitcairn, 324 U. S. 117 (1945).
  See Neilson v. Lagow, 12 How. 98, 109-110 (1852).
  See, e. g., Jennings v. Illinois, 342 U. S. 104 (1951); Loftus v. Illinois, supra; Herb v. Pitcairn, supra. Minnesota v. National Tea Co., 309 U. S. 551 (1940); Honeyman v. Hanan, 300 U. S. 14 (1937).
  Cf. Jennings v. Illinois, supra; Minnesota v. National Tea Co., supra; Honeyman v. Hanan, supra.
choices: comity: civil rights comity: criminal procedure comity: First Amendment comity: habeas corpus comity: military comity: obscenity comity: privacy comity: miscellaneous comity primarily removal cases, civil procedure (cf. comity, criminal and First Amendment); deference to foreign judicial tribunals assessment of costs or damages: as part of a court order Federal Rules of Civil Procedure including Supreme Court Rules, application of the Federal Rules of Evidence, Federal Rules of Appellate Procedure in civil litigation, Circuit Court Rules, and state rules and admiralty rules judicial review of administrative agency's or administrative official's actions and procedures mootness (cf. standing to sue: live dispute) venue no merits: writ improvidently granted no merits: dismissed or affirmed for want of a substantial or properly presented federal question, or a nonsuit no merits: dismissed or affirmed for want of jurisdiction (cf. judicial administration: Supreme Court jurisdiction or authority on appeal from federal district courts or courts of appeals) no merits: adequate non-federal grounds for decision no merits: remand to determine basis of state or federal court decision (cf. judicial administration: state law) no merits: miscellaneous standing to sue: adversary parties standing to sue: direct injury standing to sue: legal injury standing to sue: personal injury standing to sue: justiciable question standing to sue: live dispute standing to sue: parens patriae standing standing to sue: statutory standing standing to sue: private or implied cause of action standing to sue: taxpayer's suit standing to sue: miscellaneous judicial administration: jurisdiction or authority of federal district courts or territorial courts judicial administration: jurisdiction or authority of federal courts of appeals judicial administration: Supreme Court jurisdiction or authority on appeal or writ of error, from federal district courts or courts of appeals (cf. 753) judicial administration: Supreme Court jurisdiction or authority on appeal or writ of error, from highest state court judicial administration: jurisdiction or authority of the Court of Claims judicial administration: Supreme Court's original jurisdiction judicial administration: review of non-final order judicial administration: change in state law (cf. no merits: remand to determine basis of state court decision) judicial administration: federal question (cf. no merits: dismissed for want of a substantial or properly presented federal question) judicial administration: ancillary or pendent jurisdiction judicial administration: extraordinary relief (e.g., mandamus, injunction) judicial administration: certification (cf. objection to reason for denial of certiorari or appeal) judicial administration: resolution of circuit conflict, or conflict between or among other courts judicial administration: objection to reason for denial of certiorari or appeal judicial administration: collateral estoppel or res judicata judicial administration: interpleader judicial administration: untimely filing judicial administration: Act of State doctrine judicial administration: miscellaneous Supreme Court's certiorari, writ of error, or appeals jurisdiction miscellaneous judicial power, especially diversity jurisdiction