These should be taxed. Then refunded once and if senders can prove income properly reported and taxes withheld. Put a 50% tax to cover action and help build the wall.
Hell, remit a portion of that tax to Americans who've lost their jobs, or who've seen their wages plummet, due to illegals in the workforce.
I've suffered personal injury to the tune of at least a million dollars, because of our government's intentional non-enforcement of our immigration laws.
I can't even properly express my rage over this subject.