A group of retired generals and admirals also wrote a letter to Senate Democrats, saying they're "alarmed" by the provision.
"By trying terrorist suspects in civilian courts we deprive them of the warrior status they crave and treat them as the criminals and thugs they are," they wrote.
But the provision appeared in the omnibus bill anyway. A spokesman for the committee's ranking member, Sen. Thad Cochran, told TPM that minority staff did have a chance to work on the bill, so it wasn't written solely by Dems.
There's also a slight change in the language. The Senate provision includes language that it will be preempted by any "provision regarding the release or transfer of detainees" included in the Defense Authorization bill. That bill includes one provision about Gitmo, banning the transfer of detainees to a handful of countries, including Afghanistan, Pakistan and Yemen, where al Qaeda is known to operate. It's unclear if that provision would nullify the omnibus ban.
The Justice Department declined to comment on the Senate bill. Majority Leader Harry Reid's office declined to comment on whether he will try to strip the measure.
A spokesman for Minority Leader Mitch McConnell told TPM that McConnell "strongly opposes bringing any terrorists to the U.S., for trial or otherwise."
Republicans are, however, vocally opposed to the overall spending bill, and McConnell has called for his caucus to reject it.