That would depend on some of the following factors.
What were they convicted of?
Did they serve the time required for that conviction.
Did the state or municipality they committed the crime in seek any additional punishment?
Was the country they came from willing to take them back?
You see, these are key facts none of the articles you alarmist bring up.
The Ax Murderer? Yeah, I want him in OUR prison, not Mexico's.
The guy who pinched an IPod off a store kiosk because the clerk wasn't paying attention? Meh, not so much.