The Trump administration will require immigrants without legal status to register and give their fingerprints to authorities as part of its crackdown on border crossings. Anyone 14 or older who has been in the U.

The move, which could expose unregistered migrants to criminal prosecution, represents a drastic escalation of the administration’s efforts to push millions of immigrants to leave on their own.

But lawyers and immigrant advocates warned that the administration’s plan was on shaky legal ground and that some immigrants may be afraid to comply.