SINCE THE OUTSET of the war on terrorism, the Bush administration, across a wide range of issues, has had a simple message for the federal judiciary: Trust us and don't interfere. Yesterday, in a pair of much-awaited rulings, the court delivered its response. First, the justices declared that U.S. citizens designated as enemy fighters are entitled to a "fair opportunity" to challenge their detentions and "unquestionably [have] the right to access to counsel" in doing so. Then the justices held that federal courts have jurisdiction to hear challenges to the detentions of noncitizens held at Guantanamo Bay, Cuba. Trust, even during wartime, has limits.

The most important decision of the day came in the case of Yaser Esam Hamdi, the Louisiana-born Saudi man who has been held in a military brig for the past two years after being captured in Afghanistan. The decision is more historic still for transcending the court's frequent ideological divide. Eight justices rejected the government's contention that Mr. Hamdi could be locked up indefinitely, incommunicado, on the strength of a two-page, hearsay affidavit and without any opportunity to respond to the government's allegations.

The justices did not agree on the proper resolution of the case: A four-member plurality led by Justice Sandra Day O'Connor held -- as we have argued -- that an American who fights with the enemy may be detained as an enemy fighter but must have a meaningful opportunity to contest the designation. Justices David H. Souter and Ruth Bader Ginsburg argued that Congress's authorization of the use of force did not include the authority to detain Americans. Justices Antonin Scalia and John Paul Stevens argued that Mr. Hamdi was entitled either to be tried or freed. Only Justice Clarence Thomas would have affirmed the government's position.

Consequently, the case not only guarantees that Mr. Hamdi will get to tell the courts his side of the story but also sends a powerful message that Americans cannot just disappear at the hands of their government. Even during wartime, the government must be held to account -- albeit not necessarily in a full-fledged criminal trial -- before an American can be locked up. That's important not just for Mr. Hamdi but for liberty generally. And it means that the other American held as an enemy combatant, Jose Padilla, will at last get a hearing as well. The court dismissed Mr. Padilla's case, finding that it had been filed in the wrong court. But the decision in Hamdi means that in any renewed litigation, more than the government's say-so will be needed to keep Mr. Padilla behind bars.

The court's skepticism about the government's position extended even to that case where precedent was most strongly on the administration's side. The government had a powerful argument that Guantanamo lies outside the court's jurisdiction, an argument with which we agreed. Yet the administration's willful failure for so long to construct at Guantanamo a review process in which the public could have confidence makes the court's decision to intervene something of a self-inflicted wound for the administration.

It isn't clear what, in practice, the decision will mean. If the result is to spur the administration to improve review and inject a measure of outside oversight, it could prove constructive. But there are dangers as well. Holding that jurisdiction exists to consider these cases is not the same as saying they have legal merit, so the decision is far from a promise of meaningful review of Guantanamo detentions, and it could prove quite disruptive. The decision's logic seems to imply that any detainee held anywhere by U.S. forces -- even someone such as Saddam Hussein or Khalid Sheik Mohammed -- could have access to U.S. courts. However irresponsible the executive branch has been, the judiciary is ill-positioned to manage every overseas detention.

What should be clear, however, is that the judiciary will not sit still for assertions of unbridled executive power. As the war on terrorism progresses, the administration will need -- at long last -- to submit to the oversight and transparency it has so assiduously resisted.