After the jury convicted petitioner Custis of possession of a firearm by a felon and another federal crime, the Government relied on his prior state court convictions for robbery in Pennsylvania and for burglary and attempted burglary in Maryland to support a motion under the Armed Career Criminal Act of 1984, 18 U.S.C. 924(e) (ACCA), which provides for enhancement of the sentence of a convicted firearms possessor who "has three previous convictions . . . for a violent felony or a serious drug offense." Custis challenged the use for this purpose of the two Maryland convictions on the ground, among others, of ineffective assistance of counsel during the state prosecutions, but the District Court held that 924(e)(1) provides no statutory right to challenge such convictions, and that the Constitution bars the use of a prior conviction for enhancement only when there was a complete denial of counsel in the prior proceeding. Custis was sentenced to an enhanced term of 235 months in prison, and the Court of Appeals affirmed.

Held:

1. With the sole exception of convictions obtained in violation of the right to counsel, a defendant in a federal sentencing proceeding has no right to collaterally attack the validity of previous state convictions that are used to enhance his sentence under the ACCA. Pp. 4-12.

(a) Congress did not intend to permit collateral attacks on prior convictions under 924(e). The statutes language - which applies to a defendant who has "three previous convictions" of the type specified - focuses on the fact of the conviction, and nothing therein suggests that the prior final conviction may be subject to attack for potential constitutional errors before it may be counted. Page II That there is no implied right of collateral attack under 924(e) is strongly supported by 921(a)(20), which provides that a court may not count a conviction "which has been . . . set aside" by the jurisdiction in which the proceedings were held, and thereby creates a clear negative implication that courts may count a conviction that has not been so set aside; by the contrast between 924(e) and other related statutes that expressly permit repeat offenders to challenge prior convictions that are used for enhancement purposes, see, e.g., 21 U.S.C. 851(c); and by Lewis v. United States, 445 U.S. 55, in which this Court held that one of the predecessors to the current felon in possession of a firearm statute did not allow collateral attack on the predicate conviction. Pp. 4-8.

(b) The right, recognized in Burgett v. Texas, 389 U.S. 109, and United States v. Tucker, 404 U.S. 443, to collaterally attack prior convictions used for sentence enhancement purposes cannot be extended beyond the right, established in Gideon v. Wainwright, 372 U.S. 335, to have appointed counsel. Since Johnson v. Zerbst, 304 U.S. 458, and running through Burgett and Tucker, there has been a theme that failure to appoint counsel for an indigent defendant was a unique constitutional defect. None of the constitutional violations alleged by Custis, including the claimed denial of effective assistance of counsel, rises to the level of a jurisdictional defect resulting from the failure to appoint counsel at all. This conclusion is supported by the interest in promoting the finality of judgments and avoiding delay and protraction of the federal sentencing process, and by the relative ease of administering a claim of failure to appoint counsel, as opposed to other constitutional challenges. Pp. 8-12.

2. However, Custis, who was still "in custody" for purposes of his state convictions at the time of his federal sentencing under 924(e), may attack his state sentences in Maryland or through federal habeas corpus review. See Maleng v. Cook, 490 U.S. 488. If he is successful in attacking these state sentences, he may then apply for reopening of any