The answer emerged gradually, but by the end of the tightly packed 90 minutes, it was fairly clear: highly protective.
At least five justices — John Paul Stevens, Anthony M. Kennedy, David H. Souter, Ruth Bader Ginsburg, and Stephen G. Breyer — appeared ready to reject the administration's argument that the Detainee Treatment Act, passed and signed into law after the court accepted the case in November, had stripped the court of jurisdiction.
It was less certain by the end of the argument how the court would then go on to resolve the merits of the case, a multipronged attack on the validity of the military commissions themselves and on their procedures. Lawyers for the former driver, a Yemeni named Salim Ahmed Hamdan, also argue that the crime of conspiracy with which he has been charged cannot properly be tried before any military commission because it is not recognized as a war crime.
Solicitor General Paul D. Clement was on the defensive throughout his argument. His stolid refusal to concede that any of the government's positions, on the jurisdictional question as well as the ultimate questions, might present even theoretical problems provoked the normally soft-spoken Justice Souter into a mixture of rage and despair.
What appeared to trouble Justice Souter the most was Mr. Clement's assertion, in answer to a question from Justice Stevens, that by removing the federal courts' jurisdiction to hear habeas corpus petitions from detainees at the United States naval base at Guantánamo Bay, Cuba, Congress might be understood to have "suspended" the writ of habeas corpus.
This is an action limited by the Constitution to "cases of rebellion or invasion." Habeas corpus is the age-old means by which prisoners can get into court to challenge the lawfulness of their confinement, and its suspension is historically regarded as a serious, if not drastic, step.
Mr. Clement's position was that Congress had not suspended habeas corpus, but that it might constitutionally have done so given "the exigencies of 9/11." Addressing Justice Stevens, the solicitor general said: "My view would be that if Congress sort of stumbles upon a suspension of the writ, that the preconditions are satisfied, that would still be constitutionally valid."
Justice Souter interrupted. "Isn't there a pretty good argument that suspension of the writ of habeas corpus is just about the most stupendously significant act that the Congress of the United States can take," he asked, "and therefore we ought to be at least a little slow to accept your argument that it can be done from pure inadvertence?"
When Mr. Clement began to answer, Justice Souter persisted: "You are leaving us with the position of the United States that the Congress may validly suspend it inadvertently. Is that really your position?"
The solicitor general replied: "I think at least if you're talking about the extension of the writ to enemy combatants held outside the territory of the United States —"
"Now wait a minute!" Justice Souter interrupted, waving a finger. "The writ is the writ. There are not two writs of habeas corpus, for some case and for other cases. The rights that may be asserted, the rights that may be vindicated, will vary with the circumstances, but jurisdiction over habeas corpus is jurisdiction over habeas corpus."
Justice Breyer, in his questioning of Mr. Clement, practically begged the solicitor general to endorse an alternative approach that would permit the court to avoid "the most terribly difficult and important constitutional question of whether Congress can constitutionally deprive this court of jurisdiction in habeas corpus cases."
The alternative at hand was the one offered by Mr. Hamdan's lawyer, Neal Katyal, a law professor at Georgetown University. That was to interpret the Detainee Treatment Act as applying only prospectively, stripping federal courts of hearing future cases brought by the Guantánamo detainees but permitting at least the Supreme Court to continue with this one.
The argument was a textual one, based on a slight change in wording of the measure that became the Detainee Treatment Act, as originally proposed by Senator Lindsay Graham, Republican of South Carolina, and the version the Senate eventually passed after Senator Carl Levin, a Michigan Democrat, and others raised objections to taking the Hamdan case away from the Supreme Court.
Senator Graham, who filed a brief in this case, and the Bush administration maintain that the change was immaterial. But the justices appeared ready to embrace the ambiguity if it would permit them to retain jurisdiction and proceed with the case.
Only eight justices will vote in the case, Hamdan v. Rumsfeld, No. 05-184. Chief Justice John G. Roberts Jr. is not sitting, because he was a member of the three-judge panel of the federal appeals court here that rejected Mr. Hamdan's challenge to the military commissions in a decision last July.
Of the other members of the court, Justice Antonin Scalia appeared most supportive of the Bush administration. He intervened several times to offer Mr. Clement a helping hand, something the skillful solicitor general rarely needs but this time accepted gratefully.
For example, Justice Kennedy was questioning Mr. Clement on the government's position that even if the court had jurisdiction, it should abstain from ruling on the validity of the military commission until after Mr. Hamdan's trial. Justice Kennedy said he found the argument troubling, pointing out that Mr. Hamdan was challenging a "structural invalidity to the military commission," its lack of compliance with protections guaranteed by the Geneva Conventions.
"The historic office of habeas corpus is to test whether or not you're being tried by a lawful tribunal," Justice Kennedy continued. "And he says, under the Geneva Convention, as you know, that it isn't."
Mr. Clement replied that Mr. Hamdan could raise that argument, which he predicted would fail, before the military commission itself. There was no reason "why that claim has to be brought at this stage in the procedure," he said.
Justice Scalia then intervened, observing that "I thought we established earlier" that "in the normal criminal suit, even if you claim that the forum is not properly constituted, that claim is not adjudicated immediately." Rather, "it's adjudicated at the conclusion of the proceeding," the justice continued.
"Well, of course, that's true," Mr. Clement said.
Justice Scalia went on: "We don't intervene on habeas corpus when somebody says that the panel is improperly constituted. We wait until the proceeding's terminated, normally."
"That's exactly right, Justice Scalia," Mr. Clement said.
Justice Kennedy objected. "Is that true?" he aside. "If a group of people decides they're going to try somebody, we wait until that group of people finishes the trial before the court intervenes to determine the authority of the tribunal?"
"With respect, Justice Kennedy, this isn't 'a group of people,' " Mr. Clement replied. "This is the president invoking an authority that he's exercised in virtually every war that we've had."
Along with Justice Scalia, Justice Samuel A. Alito Jr. also appeared interested in the argument that the court should permit the trial to go forward. Justice Clarence Thomas alone asked no questions during the argument.
Mr. Clement asserted that the Detainee Treatment Act would allow a detainees to argue in federal court, after conviction by a military commission, that the commission's procedures were illegal or unconstitutional.
Justice Ginsburg then asked him to "straighten me out." She said, "I thought it was the government's position that these enemy combatants do not have any rights under the Constitution and laws of the United States."
"That is true, Justice Ginsburg," the solicitor general answered.
Mr. Hamdan's lawyer, Mr. Katyal, appeared to get considerable traction with his argument that the crime of conspiracy, with which Mr. Hamdan and nine other detainees awaiting military commissions have been charged, is not an appropriate crime for trial before a military commission. If a majority agrees, this might provide a narrow way of resolving the case.
In many respects, the argument marked a resumption of the encounter between the court and Bush administration two years ago, in cases that led to the court's rejection of the administration's claim to broad authority to proceed without judicial oversight. The administration was once again seeking "fundamentally open-ended authority," the "blank check" the court had rejected then, Mr. Katyal said.