Fingerprinting them upon departure should be one good way to make sure they don’t return.
Yeah like that is going to happen. Even if they did fingerprint them criminals here are fingerprinted and they still commit crimes and disappear from justice.
Yuuge wall, deport, let everyone apply legally, select those that would fit in society for legal immigration(as it should have been anyway). Some of those applying may have once been illegal. Many won’t have been. But all coming here need to assimilate, obey laws or get out.