Children play a game called "opposite day." Whatever someone says is taken to mean the opposite. Some Supreme Court justices have apparently never grown out of their appreciation of this game, to judge by their ruling in the Hamdan case involving military tribunals at Guantanamo Bay.

Last year, Congress (you might have heard of it — it writes the nation's laws) passed a bill signed into law by the president of the United States (he also should be familiar — the nation's commander in chief). It said that "no court, justice or judge" shall have the jurisdiction to consider habeas corpus applications of detainees at Gitmo. It would take a legal escape artist on par with David Blaine to wiggle out of that one, but, sure enough, five Supreme Court justices were up to the task.

The Supreme Court has an important role in our constitutional scheme, but it is not fit to, nor was it ever meant to, render fundamental judgments about matters of war and peace. For that we have the elected branches, primarily the executive, which has the flexibility and the focus to prosecute wars. But today's court knows no bounds.

In writing for the majority in Hamdan, Justice John Paul Stevens ripped off his black robe and beat his chest, declaring to the world, "Stand aside Congress, stand aside Mr. President, you constitutional weaklings. We, the court, can win the War on Terror and will do it with judicial overreaching, tendentious statutory construction and implausible renderings of international law."

The saving grace of Hamdan is that it preserves the option of trying al-Qaida members before military commissions, as long as Congress and the president work to craft the commissions just so. Otherwise, the decision is a disgrace and is a step toward affording members of al-Qaida the full panoply of rights and protections criminal suspects enjoy in the American civil court system.

Or, as Nancy Pelosi put it in a statement hailing the decision, it "reaffirms the American ideal that all are entitled to the basic guarantees of our justice system." That "all" is quite literal, whether someone is a foreigner or an American, an al-Qaida warrior or a shoplifter. Never have enemy fighters — especially fighters belonging to a criminal band with no regard for the laws of war — had it so good.

The court moves in this direction by effectively reading al-Qaida into the Geneva Conventions. The conventions are a treaty to which nations voluntarily bind themselves. Al-Qaida has never signed on, since 1) it isn't a nation; and 2) it would be an obstacle to practices that are central to its organization, including slaughtering civilians and beheading prisoners. But the court bestows a bonus membership to al-Qaida, because it furthers the court's goal of dictating how captured al-Qaida members should be tried.

It's not that the court's reading of the Geneva Conventions is entirely implausible, but that the president has another, more reasonable reading of Geneva that there is no reason for the court to trample on. But trample it does, a quality of its decision throughout.

Justice Clarence Thomas writes in dissent, "Those Justices who today disregard the commander-in-chief's wartime decisions, only 10 days ago deferred to the judgment of the Corps of Engineers with regard to a matter much more within the competence of lawyers, upholding that agency's wildly implausible conclusions that a storm drain is a tributary of the water of the United States. It goes without saying that there is much more at stake here than storm drains."

From its conclusion that Geneva applies to al-Qaida, the court works its way toward mandating that military commissions must duplicate the structure of courts-martial. This in itself needn't be disastrous, but the court is on a dangerous path. The decision sets the table for more severe judicial interference in the war-making of the executive branch and Congress. Justice Stevens surely has many impressive talents, but fighting al-Qaida isn't one of them.