Guantanamo-like indefinite detention is hardly new
stuckk.net
stuckk.net
The trickier problem though is just what do we do with bad people that nobody wants. If we don't want to admit them and no one else will take them, can we then indefinitely detain them or are we obligated by some common sympathy to eventually let them in? I'm not sure but I'm inclined towards the latter.
If that's the case then we lose nothing by granting potential parolees legal alien status.