It so happens that the vast majority of those being held...with identities withheld for various (good) reason are non-citizens...and are already being held for violations of US law. We, if most of the info is true, don't need to try them to deport them.
Would they qualify in the definition of who could be put into a tribunal. Probably.
Whats so slippery about the slope? Unless they apply it to citizens...I've got pretty firm grip on the ground.