Soon after 9/11, George W. Bush, addressing Congress, said of our murderous enemies, "They hate our freedoms!" But on Oct. 17, 2006, Bush -- following the path charted by Dick Cheney, Donald Rumsfeld and then-Attorney General Alberto Gonzales -- took pride in signing the Military Commissions Act of 2006 into law, which, especially in one part, dangerously diminishes an essential individual liberty under the Constitution.

Last June, the Supreme Court reversed one section of the MCA that prohibited terror suspects held at Guantanamo from using habeas corpus to petition our civilian courts. But still in this law is a section authorizing the president to designate as an "enemy combatant ... a person," including an American citizen, "who has engaged in hostilities or who has purposely and materially supported hostilities against the United States." Lawful permanent noncitizens living here can also be made to fit that forbidding definition.

Charlie Savage, who won a Pulitzer Prize for meticulously exposing Bush's unprecedentedly abundant use of "signing statements" after he had signed a bill into law -- allowing him to not follow that law -- wrote in his invaluable book, "Takeover: The Return of the Imperial Presidency and the Subversion of American Democracy" (Little Brown):

"Under the Military Commissions Act, the president (now including Barack Obama) can seize citizens as enemy combatants even if they have nothing to do with Al Qaeda" because "an enemy combatant can be anyone 'who has purposefully and materially supported hostilities against the United States.'"

As Savage, now with The New York Times, said to me recently, "Yes, indeed, that is still in the law." How many American know that? Does Obama?

The Military Commissions Act was passed by the 2006 Republican-controlled Congress with the support of a sizable number of Democrats, leery of being targeted as "soft on terrorism." But one of its most passionate opponents was Democratic Sen. Patrick Leahy of Vermont, for whom I'd have voted enthusiastically if he'd ever run for president.

Said Leahy, during debate on the Senate floor: "Imagine you are a law-abiding, lawful permanent resident. ... You do charitable fundraising for international relief agencies. ... Then one day there is a knock at your door. The government thinks that the Muslin charity you sent money to may be funneling money to terrorists, and it thinks you may be involved." As a suspected enemy combatant, you can bring your toothbrush to prison.

I have seen many lists, and they're still coming, from civil liberties and human-rights organizations, among other groups, on what our new president and Congress must do to resuscitate the Bill of Rights and other parts of the Constitution.

But I have not yet seen on any list the need for Obama and the now enlarged Democratic majority in Congress to protect us from such vague, slippery language as "purposefully and materially" that could send Americans utterly uninvolved in terrorism to a prison cell as "enemy combatants."

During the next four years, or under a subsequent president, a series of jihadist equivalents of 9/11 attacks could ignite a terrified Congress, listening to a terrified citizenry, to demand that this definition of an "enemy combatant" be implemented swiftly and actively.

The libertarian Cato Institute's Gene Healy -- author of a valuable, serious study, "The Cult of the Presidency: America's Dangerous Devotion to Executive Power" (Cato), made a sobering point Feb. 4:

"Barack Obama has done more than any candidate in memory to boost expectations for the (presidential) office." But, "if and when a car bomb goes off somewhere or something much worse in America, would a President Obama be able to resist resorting to warrantless wiretapping (which he's already voted for as a senator), undeclared wars or the Bush theory of unrestrained executive power? As a Democrat without military experience, publicly perceived as weak on national security, (Obama) would have much more to prove (to the citizenry)."

An even more troubling cautionary note comes from Jack Goldsmith who, while in the Bush Justice Department, tried hard to roll back that administration's conviction that in the war on terrorism, there are times when only the president must be the law. He is the author of "The Terror Presidency" (W.W. Norton).

Goldsmith, as quoted by Healy in Reason magazine, warns: "For generations, The Terror Presidency will be characterized by an unremitting fear of attack, an obsession with preventing the attack, and a proclivity to act aggressively and pre-emptively to do so."

A future president will be aware, Goldsmith predicted, that "he alone will be wholly responsible if thousands of Americans are killed in the next attack." That includes Obama.

So whether actual terror does strike at home now or maybe in the administration of Sarah Palin, it's vital for the present commander in chief and Congress to change the Military Commissions Act so that those of us allegedly purposefully and materially supporting hostilities against the United States -- without any evidence to support that charge -- do not flood our prisons. Do we want to go back to the Japanese-American interment camps of World War II?

Nat Hentoff is a nationally renowned authority on the First Amendment and the Bill of Rights and author of many books, including "The War on the Bill of Rights and the Gathering Resistance" (Seven Stories Press, 2004).

(Nov. 12, 2008)