Glenn Greenwald is right to point out that Barack Obama had embraced military commissions and indefinite detention before Congress put an end to transfers of Gitmo detainees to the U.S. for trial. But on the issue of Gitmo, I think he really understates Congress' role--the funding for closing the facility could have been secured very early on if the administration had been prepared and if Dems in Congress had been less skittish.
The argument for codifying indefinite detention--made most persuasively by Ben Wittes--goes something like this: Acknowledging that this is a hole of the administration's own making, isn't the fact that the Periodic Review Board process is becoming more adversarial a good thing? For the past two years we've had indefinite detention without periodic review. Now some of the detainees who have lost their habeas cases are going to get a chance to challenge their detention again, and they have the option of being represented by council. The argument for an executive order is that going to Congress might make the current process significantly worse, since Republicans have indicated a desire to send more people to Gitmo and to give the president to indefinitely detain American citizens.
So now that there's no question that some people will be detained indefinitely, the people who lose their habeas cases should have a chance to advocate for their freedom. Proponents could say that this is like the argument that fewer people would have sex if abortion or contraception were less available. The truth is people are going to have sex anyway, and the government has an interest in making sure people have access to the things that can protect them from disease or unwanted pregnancy. If we're going to be doing indefinite detention, these people should have a chance to argue that they do not or no longer need to be detained.
But of course the analogy doesn't quite work, because of course we don't have to do indefinite detention. It's a conscious decision being made by the government, not a social phenomenon government can only mitigate the negative effects of rather than really control. We shouldn't be doing it. There's a narrower argument one could make that because the EO is limited to the "legacy cases," that it's just about cleaning up a mess left over by the Bush administration. But this amounts to detaining some people in part because they were abused by the government.
There's a longstanding precedent for military detention authority. But the "war on terror" is not a conventional war, and its "warriors" don't readily identify themselves or wear uniforms, so determining who can be lawfully detained is no simple task. That authority can be more clearly applied to people captured on battlefields in Afghanistan and Iraq, less so to those who have spent years in a detention camp in the Caribbean. As Ken Gude notes, the new EO states that the PRB will only detain those who are considered "significant threat to the security of the United States."
But that just begs the question. If they're so clearly a "significant threat," why aren't we just trying them in the first place?