IMO, its one of law's thats there to scare people and would be rarely enforced by officers, immigrants now know this new law so they would think twice before entering, but police are human they dont want to appear racist so they probably will never ask ID for the sole reason of "u look mexican bro"
here in NZ when the anti smacking bill came out (against the law to parent you child through physical punushment) people were against it completely, its there to stop child beaters, and has been used only once in court
my 2 cents