From the initial returns, one might believe that the Bush administration suffered a legal defeat this week in the war against terrorism. In Rasul v. Bush, the Supreme Court ruled that the federal courts--for the first time--will review the grounds for detaining alien enemy combatants held outside the U.S. In Hamdi v. Rumsfeld, the justices required that American citizens detained in the war have access to a lawyer and a fair hearing before a neutral judge.

But despite the pleas of legal and media elites, the justices did not turn the clock back to Sept. 10, 2001. While the Court has unwisely injected itself into military matters, closer examination reveals that it has affirmed the administration's fundamental legal approach to the war on terrorism, and left it with sufficient flexibility to effectively prevail in the future.

To wit, the Court agreed that the U.S. is at war against the al Qaeda terrorist network and the Taliban militia that supports them. It agreed that Congress has authorized that war. Moreover, the justices implicitly recognized that the U.S. may use all of the tools of war to fight a new kind of enemy that has no territory, no population and no desire to spare innocent civilian life.

Taken as a whole, the Court's message is unmistakable: The days when terrorism was merely considered a law enforcement problem and our only forces were limited to the FBI, federal prosecutors and the criminal justice system will not be returning.

Following judicial precedent and common sense, a plurality of four justices in Hamdi agreed that waging war must include the power to detain enemy combatants. Justice O'Connor's opinion made clear that detention in wartime is not a punishment, and so does not deserve the trappings and procedures of the domestic criminal-justice system. As she observed, "the purpose of detention is to prevent captured individuals from returning to the field of battle and taking up arms once again." Enemy combatants can even include American citizens who join al Qaeda or the Taliban. Brushing aside the argument that Yaser Hamdi's detention was illegal because it was indefinite, the Court affirmed that an enemy combatant may be detained for as long as active hostilities continue, as they do in Afghanistan.

Upholding the detention of citizens who join the enemy is perhaps the most significant aspect of this week's opinions. As the José Padilla example shows, al Qaeda has been recruiting American citizens who can better escape detection. While fighting there continues, Afghanistan will not be the frontline of the future; O'Hare airport, New York Harbor and the Mexican and Canadian borders will be. Preventing the government from detaining citizens who have decided to become terrorists would have seriously handicapped the nation's ability to stop attacks and to gain better intelligence on our enemy's plans.

Although Justice O'Connor's opinion was joined only by Chief Justice Rehnquist and Justices Kennedy and Breyer, her conclusions on these points were shared by Justice Thomas. They parted ways, however, in deciding what happens once the enemy combatant challenges his detention. All agree (including the government) that the federal courts should review detentions through habeas corpus; the disagreements occurred over how much proof the government has to show, whether and when the detainee would receive a lawyer, and the type of hearing required. Justice Thomas, who properly found that courts "lack the expertise and capacity to second-guess" the battlefield decisions made by the military and ultimately the president, would have asked the government to show some evidence why a detainee qualifies as an enemy combatant.

In what can be seen as naiveté, or as "constitutional improvisation" designed "to increase the power of the Court," (Justice Scalia's words), the plurality went further and imposed vague guidelines for reviewing detentions. Rejecting the positions of both Hamdi and the government, it struck the compromise that an enemy combatant must receive a lawyer and "a fair opportunity to rebut the Government's factual assertions before a neutral decisionmaker." Even then, it found that the government should receive a presumption in favor of its evidence, one that put the burden of proof on the detainee to disprove.

Nevertheless, the Justices left the hard questions up to the lower courts and the administration, or even Congress, to resolve. This is especially important in light of the decision in Rasul, a clear defeat for the government, in which the Court found that Guantanamo Bay (and perhaps military operations world-wide) lay within the jurisdiction of the federal courts. Rasul essentially overruled the 1950 Supreme Court case upon which the government had relied in locating its detention facility there, and it threatens to inject the federal courts into the micromanagement of the military.

While we can expect the 600 detainees to each file a habeas petition, possibly in each of the 94 district courts, Rasul gives no guidance on how soon those hearings must be held, where they will be held, who can participate and how classified intelligence will remain protected. Despite an extended discussion of the peculiarities of the Guantanamo lease, Rasul leaves unclear whether judicial review would apply beyond Guantanamo to Iraq (and Saddam Hussein) or Afghanistan (and Osama bin Laden, should he be captured).

Nonetheless, rather than view these cases as a defeat, the administration should see them as an opportunity. While it has unwisely extended its reach to wartime detentions outside the U.S., the Court has left the executive branch with substantial room to maneuver on the nature and scope of review: Hamdi approves of a detainee's access to counsel, but does not explain when they can meet, whether their communications can be monitored for clandestine messages, or whether the lawyers can be military officers; Rasul studiously avoided any discussion of the substantive rights, if any, that al Qaeda and Taliban detainees have; and neither overturned the administration's policy that the Geneva Conventions do not apply. (And yesterday, in Sosa v. Alvarez-Machain, the Court expressed great skepticism about the ability of federal courts to enforce international law norms without the permission of Congress.)

The Pentagon could easily adapt its existing review process for Guantanamo prisoners to meet the Hamdi standards (as Justice O'Connor seemed to invite), which surely must equal if not exceed those required for alien enemy combatants. Military commissions already established to try alien terrorists would almost certainly meet the procedural requirements set out by the Court.

Because of the judiciary's unprecedented expansion into what had always been considered the ultimate preserve of the political branches, the executive will have to do a better job of reviewing its detention cases and explaining its reasons. Now is the time for Congress and the president, vested by the Constitution with all of the war power and directly elected by the American people, to establish these procedures with a broader view of the costs and benefits for the war on terrorism. They should not wait for district judges to make these choices ad hoc simply because they happen to hear the early cases.

So far, the president and Congress still have the opportunity to make these fundamentally military choices in a way that may not interfere with important battlefield decisions. Whatever the policies chosen, however, they will require the devotion of more resources toward lawyers and judges and less to direct military operations or intelligence-gathering. That, alas, is the price of satisfying an imperial judiciary.

John Yoo is a visiting scholar at the American Enterprise Institute.