Are you putting that forth as a serious argument? because the facts are certainly bogus. If it was even half true it wouldn't hold water because they certainly wouldn't make a law retroactive to employers.
The law has been on the books for a long time and it's unenforceable.
Did you ask for your gardener's papers, and even if you would, how do you know whether they are real or forgeries?
As I said, the answer is to stop them at the border, instead of expecting private people or business people to become forder enforcement agents.