Legal Question in Constitutional Law in Florida

Immigrants who are ordered removed from the U.S. but whose countries will not take them back are held in federal custody. Most of the people currently in that situation are Cubans.

You are right that many of them are criminals who have completed their prison terms. But that does not entitle them to stay in the U.S. if they have been properly ordered to leave the country. Similarly-situated immigrants from other countries are deported at the end of their prison terms. Treating the ones from Cuba more favorably would not be just, and it would give other countries an incentive to refuse the return of their citizens the way Cuba now does.