Non-convicted persons, not "non-criminals"

https://www.law.cornell.edu/uscode/text/8/1325

Illegal entry is still a crime.

Innocent until proven guilty. Nobody is a criminal until some judge declared them to be.

Criminals are people who commit crimes generally, not just people who have been convicted of them. You can independently be charged with harboring a criminal awaiting trial regardless of their adjudication status.