"The law requires the defense secretary to notify relevant congressional committees at least 30 days before making any transfers of prisoners, to explain the reason and to provide assurances that those released would not be in a position to reengage in activities that could threaten the United States or its interests."
On Obama's side, the argument is that the statute is unconstitutional, a congressional encroachment on presidential power. There's no way to undo the exchange, and acting in secrecy, without informing Congress, is an exercise of the very power that the President says the statute violates. Taking this action embodies an argument that this power does and should rest with the President. Is there anything that can be done now to press the opposing argument? We can criticize the President, as we always already do. The only other alternative I see is to impeach the President.
Go ahead. He's daring you. Perhaps part of his motivation for the prisoner trade was a predicted political boost as the President's opponents are distracted into seeming to complain about the return of a hero and tripping all over themselves as they posture about impeachment.
ADDED: Proofreading, Meade reads the post title and says: "What does that remind you of? Iran-Contra."
AND: I had a second update that I accidentally deleted. This is an attempt to reconstruct it. What I'd said was that the 5 Taliban leaders might be more useful to America on the loose than in detention, quite aside from concerns about closing or minimizing Guantanamo, because if they are out and about, we can conduct surveillance on them and, if they do anything that the President finds threatening, he can use his drones to kill them, according to his drone program. Since they know that, they may avoid doing anything, and if they reconnect with other terrorists, they may create even better targets for the drone program. That is, there are levels of wisdom and deviousness here that we can't know.