Its kind of like breathalyzer laws. If you get pulled over for a illegal u-turn or a non-dui related issues and then a officer has a suspicion to believe you have been drinking he can require you to take a breathalyzer, in VA. In VA you have to submit to breathalyzers as part of your agreement to hold a drivers license.
So this just requires non-citizens to carry documentation papers with them at all times, but citizens do not have to. As long as police cannot approach someone or detain them on suspicion of being illegal, and as long as citizens or people the police cannot verify are illegal are immediately sent on their way I got no beef with the law. If you get stopped for doing something wrong police should be able to verify someone’s right to live here.
I remember seeing this sign when i visited CA early this year:
stock photo - Caution:Illegal Immigrant Crossing
They dont put these signs up because there isnt a serious problem going on. These states have to do something.