Robert Chesney, with a great catch, notes that Congress is about to make it happen as part of a resolution to continue funding the federal government:
SEC. 1116. None of the funds made available in this or any prior Act may be used to transfer, release, or assist in the transfer or release to or within the United States, its territories, or possessions Khalid Sheikh Mohammed or any other detainee who—
(1) is not a United States citizen or a member of the Armed Forces of the United States; and
(2) is or was held on or after June 24, 2009, at the United States Naval Station, Guantanamo Bay, Cuba, by the Department of Defense.
SEC. 2210. None of the funds provided to the Department of Justice in this or any prior Act shall be available for the acquisition of any facility that is to be used wholly or in part for the incarceration or detention of any individual detained at Naval Station, Guantanamo Bay, Cuba, as of June 24, 2009.
The House is going to vote on it soon, but as Josh Gerstein notes, this would be the end of any funding for any civilian terrorism prosecutions of Gitmo detainees until at least next September. Not that the administration appears to be planning any for the near future.
No president, Republican or Democrat, would willingly sign on to this kind of interference with powers that are pretty clearly the province of the executive, unless they were absolutely forced to. It's also worth pointing out that during the five years after 9/11 that Republicans controlled both Congress and the White House, there were no efforts to prevent the Bush administration from using civilian trials to convict terrorists. The point of this resolution, though, isn't really to stop civilian prosecutions of suspected terrorists; it's to ensure that Gitmo can never be emptied.
