Do you see a problem with a law that authorizes indefinite military detention of anyone the president identifies as an enemy of the state? For President Obama, the problem is clear: The law does not give him enough discretion.

Obama has threatened to veto the National Defense Authorization Act if the final version includes a provision approved by the Senate last week that requires military detention of some terrorism suspects. Obama, like his predecessor, wants the leeway to keep them in civilian custody, and maybe even give them a trial, if he so chooses. Those of us who are not the president are apt to be more concerned about the unchecked power the bill gives him to lock us up and throw away the key.

Defenders of the bill's detention provisions say they merely codify powers granted by the Authorization for Use of Military Force (AUMF) that Congress approved after the September 11 terrorist attacks. But unlike the AUMF, Section 1031 of the National Defense Authorization Act explicitly "affirms" the legality of military detention "without trial." Furthermore, it says such treatment is permitted not only for "a person who planned, authorized, committed, or aided the terrorist attacks" or who "harbored those responsible" (language that echoes the AUMF) but also for anyone who joins or supports Al Qaeda, the Taliban, or "associated forces"—a much wider net.

Section 1032 of the bill creates a presumption in favor of military detention for a member of Al Qaeda or an allied organization who "participated in the course of planning or carrying out an attack or attempted attack against the United States or its coalition partners." But it says "the requirement to detain a person in military custody under this section does not extend to citizens of the United States."

Taken together, these two sections mean military detention is authorized but not required for U.S. citizens. As Sen. Lindsey Graham (R-S.C.), a leading supporter of the bill, put it on the Senate floor last month, "1032, the military custody provision…doesn't apply to American citizens. 1031, the statement of authority to detain, does apply to American citizens, and it designates the world as the battlefield, including the homeland."

In short, the bill asserts the president's power to snatch anyone from anywhere, including a U.S. citizen on U.S. soil, and confine him in a military prison without charge until the end of a perpetual, worldwide war against an amorphous enemy. Senators from both parties who were alarmed at that prospect tried to remove the detention provisions, but the most they could achieve was an amendment saying the bill does not "limit or expand" the president's powers under the AUMF or "affect existing law or authorities" regarding detention of people "captured or arrested in the United States."

According to its sponsor, Sen. Dianne Feinstein (D-Calif.), the amendment was intended to "declare a truce" between those who say the detention power described by Graham already exists and those who disagree. Feinstein said the amendment "leaves it to the courts to decide."

So far the government has not been eager to test the constitutionality of its detention policies. In 2004 the Supreme Court said due process required that a U.S. citizen captured on the battlefield in Afghanistan and held as an enemy combatant be given "a meaningful opportunity to contest the factual basis for that detention before a neutral decisionmaker." The Bush administration let him go instead. In the two cases where the Pentagon took charge of terrorism suspects arrested in the United States, the government likewise avoided a definitive judicial resolution, transferring them back to civilian custody before the Supreme Court had a chance to rule on their treatment.

In any case, the Feinstein amendment (which passed almost unanimously) represents an astonishing abdication of legislative responsibility. The courts should be deciding the constitutionality of the detention policy established by Congress, not sifting through deliberately ambiguous statutory language to figure out what that policy is.

Jacob Sullum is a senior editor at Reason and a nationally syndicated columnist. Follow him on Twitter.

© Copyright 2011 by Creators Syndicate Inc.