Arrests are based on suspicion. As long as there is reasonable suspicion at the time of the arrest then it’s valid.

What qualifies as "reasonable suspicion" of a citizen committing an immigration crime? Aren't you just advocating for the ability of ICE to arrest anyone who has the wrong color skin or speaks the wrong language?

isn't that the point?

Probable cause or a warrant. I am not sure what PC for being an illegal immigrant looks like, maybe seeing someone climbing the border wall?

Obviously it's being brown or speaking Spanish...

Reasonable suspicion is not a high enough bar to jail somebody.