Once we start down the road to military commissions, there's no turning back [link fixed]

The commissions can operate inside the United States, and they have jurisdiction over a broad range of crimes. Nothing in the Military Commissions Act limits the military trials to Guantanamo detainees, or to people captured and held abroad, or even to terrorism suspects. Nothing prevents the commissions from trying noncitizens, arrested inside the country, whom the president unilaterally designates as “unprivileged enemy belligerents.” In other words, the law permits military officers to try non-Americans from Alabama and Arkansas as well as Afghanistan.

The Obama administration’s decision last week to shift the high-profile 9/11 case from federal court is bound to move the military system toward legitimacy. The commissions lack the seasoned body of precedent that guides civilian courts, so their procedures will have to survive litigation by defense lawyers. But once the commissions gain stature and become the “new normal,” every future administration will have a ready instrument to arrest, judge and sentence wholly within the executive branch, evading the separation of powers carefully calibrated in the Constitution. The judicial branch has no role except on appeal, where only the federal court for the D.C. circuit may review a verdict and sentence after the trial.