dissenting.
When, at a pretrial conference, the United States District Judge assigned to this case asked petitioner’s counsel (in petitioner’s presence) whether he had “[a]ny objection to picking the jury before a magistrate,” counsel responded, “I would love the opportunity.” App. 2. Before conducting voir dire, the Magistrate herself asked counsel, “I have the consent of your client to proceed with the jury selection?” Counsel answered, “Yes, your Honor.” Id., at 5. After the jury was selected under the Magistrate’s supervision, but before it was sworn, the parties met with the District Judge to discuss unresolved pretrial matters. Neither petitioner nor his counsel raised any objection at that time — or at any other point during the trial — to the Magistrate’s role in jury selection. Two significant events transpired thereafter. First, the jury convicted petitioner on all counts. Second, after the conviction but prior to sentencing, this Court announced Gomez v. United States, 490 U. S. 858 (1989), holding that the Federal Magistrates Act did not authorize magistrates to conduct felony voir dire (in that case, where a defendant had objected). On appeal, petitioner sought to raise a Gomez claim, but the Court of Appeals held that his consent below *953precluded him from raising this newly discovered objection to the Magistrate’s role.
As a general matter, of course, a litigant must raise all issues and objections at trial. See Freytag v. Commissioner, ante, at 894-895 (Scalia, J., concurring in judgment). For criminal proceedings in the federal courts, this principle is embodied in Federal Rule of Criminal Procedure 51, which requires “a party, at the time the ruling or order of the [trial] court is made or sought, [to] mak[e] known to the court the action which that party desires the court to take or that party’s objection to the action of the court and the grounds therefor.”
Rule 51’s command is not, however, absolute. One of the hoariest precepts in our federal judicial system is that a claim going to a court’s subject-matter jurisdiction may be raised at any point in the litigation by any party. See Freytag, ante, at 896 (Scalia, J., concurring in judgment). Petitioner seeks to invoke that exception here, relying on our statement in Gomez that the Magistrate lacked “jurisdiction to preside” over the voir dire in that case, 490 U. S., at 876. But, as Judge Easterbrook has aptly observed, “ ‘jurisdiction’ ... is a many-hued term.” United States v. Wey, 895 F. 2d 429, 431 (CA7), cert. denied, 497 U. S. 1029 (1990). We used it in Gomez as a synonym for “authority,” not in the technical sense involving subject-matter jurisdiction. The judgment here is the judgment of the District Court; the relevant question is whether it had subject-matter jurisdiction; and there is no doubt that it had. The fact that the court may have improperly delegated to the Magistrate a function it should have performed personally goes to the lawfulness of the manner in which it acted, but not to its jurisdiction to act.
This venerable exception to the contemporaneous-objection rule being inapplicable here, petitioner plainly forfeited the right to advance his current challenges to the Magistrate’s role. In certain narrow contexts, however, appellate courts have discretion to overlook a trial forfeiture. The most im*954portant of these is described in Federal Rule of Criminal Procedure 52(b): In criminal cases, an appellate court may notice “errors or defects” not brought to the attention of the trial court if they are “plain” and “affec[t] substantial rights.” See United States v. Young, 470 U. S. 1, 15, and n. 12 (1985). Petitioner’s contention that this case falls into that exception comes up against our admonition that Rule 52(b) applies only to errors that are obvious as well as significantly prejudicial. See, e. g., United States v. Frady, 456 U. S. 152, 163, and nn. 13, 14 (1982). The error alleged here was anything but obvious. At the time this case was tried, the Second Circuit had held that a magistrate was authorized to conduct felony voir dire even if the defendant objected, see United States v. Garcia, 848 F. 2d 1324 (1988), rev’d sub nom. Gomez v. United States, 490 U. S. 858 (1989). No Circuit had held that it was error for a magistrate to conduct voir dire where the defendant consented. Perhaps the best indication that there was no “plain” error, of course, is that five Justices of this Court today hold that there was no error at all.*
Even when an error is not “plain,” this Court has in extraordinary circumstances exercised discretion to consider claims forfeited below. See, e. g., Glidden Co. v. Zdanok, 370 U. S. 530, 535-536 (1962) (opinion of Harlan, J.); Grosso v. United States, 390 U. S. 62, 71-72 (1968); Hormel v. Helvering, 312 U. S. 552, 556-560 (1941). In my view, that course is appropriate here. Petitioner’s principal claims are that the Federal Magistrates Act does not allow a district court to assign felony voir dire to a magistrate even with the defendant’s consent, and that in any event the consent here was ineffective because given orally by counsel and not in writing by the defendant. By definition, these claims can be *955advanced only by a litigant who will, if ordinary rules are applied, be deemed to have forfeited them: A defendant who objects will not be assigned to the magistrate at all. Thus, if we invariably dismissed claims of this nature on the ground of forfeiture, district courts would never know whether the Act authorizes them, with the defendant’s consent, to refer felony voir dire to a magistrate, and, if so, what form the consent must take. Cf. 18 U. S. C. § 3401(b) (defendant’s consent to magistrate in misdemeanor trial must be in writing).
Given the impediments to the proper assertion of these claims, I believe we are justified in reaching the statutory issue today to guide the district courts in the future performance of their duties. It is not that we must address the claims because all legal questions require judicial answers, cf. Valley Forge Christian College v. Americans United for Separation of Church and State, Inc., 454 U. S. 464, 489 (1982); Webster v. Doe, 486 U. S. 592, 612-613 (1988) (Scalia, J., dissenting), but simply that the relevant rules and statutes governing forfeiture, as we have long construed them, recognize a limited discretion which it is eminently sensible to exercise here.
Turning to the merits of the statutory claim, I am in general agreement with Justice Marshall. In my view, Gomez was driven not primarily by the constitutional problems associated with forcing a litigant to adjudicate his federal claim before a magistrate, but by ordinary principles of statutory interpretation. By specifically authorizing magistrates to perform duties in civil and misdemeanor trials, and specifying the manner in which parties were to express their consent in those situations, the statute suggested absence of authority to preside over felony trials through some (unspecified) mode of consent. The canon of ejusdem generis keeps the “additional duties” clause from swallowing up the rest of the statute. See Gomez, supra, at 872.
I would therefore conclude (as respondent in fact conceded) that district courts are not authorized by the Federal Magis*956trates Act to delegate felony voir dire to magistrates. Having reached that conclusion, I need not, and do not, answer the serious and difficult constitutional questions raised by the contrary construction. I note, however, that while there may be persuasive reasons why the use of a magistrate in these circumstances is constitutional, the Court does not provide them today. The Court’s analysis turns on the fact that courts themselves control the decision whether, and to what extent, magistrates will be used. Ante, at 937-939. But the Constitution guarantees not merely that no branch will be forced by one of the other branches to let someone else exercise its assigned powers — but that none of the branches will itself alienate its assigned powers. Otherwise, the doctrine of unconstitutional delegation of legislative power (which delegation cannot plausibly be compelled by one of the other branches) is a dead letter, and our decisions in A. L. A. Schechter Poultry Corp. v. United States, 295 U. S. 495 (1935), and Panama Refining Co. v. Ryan, 293 U. S. 388 (1935), are inexplicable.
Because I conclude that the alleged error was not “plain,” I have no occasion to assess its prejudicial impact, assuming that that is possible. Cf. Gomez v. United States, 490 U. S., at 876; Arizona v. Fulminante, 499 U. S. 279, 296 (1991).