If you ask someone if they are legal and they say "yes" are you liable if they lied?
I wish everything was on a case-by-case basis, but with that possibility, comes the happenstance of corruption and bribery from the people in question.
If any policy is made into law, someone innocent might get hurt. But if the policy/law is too lax, then there is the possibility of corruption/letting someone who isn't innocent into the system.
What would be a good balance?