How about paying back taxes?
“When did you enter the US?”
“For each year you were working in the US, did you file a Federal income tax return? A state income tax return?”
“What Social Security number did you enter on each tax return?”
“If you did any work for cash payment, did you file a Schedule C and pay self-employment tax of 15.3%?”
You forgot, “did you register for the draft?” as every male of age is required to do, legal or illegal.
Amnesty is a small word for the number of crimes they have to be absolved of.
Of course, those questions will have to first be translated into whatever dialect those "guest workers" happen to speak.