When I worked with a large university, most of the foreign students I knew had been contacted by counterfeiters and their prices were accessible. Some students wanted to stay in the US and paid for false documents. I would estimate that 90% of the illegals have false documents of some kind. The gummint has no way, they claim, to determine which are real and which are fake. It should be relatively easy to figure out how to do that.
Better yet, with an unbreakable photo ID with a thumb print for all Americans, this problem would disappear, but many resist that idea.
Anything man made can be duplicated with exacting precision.