Actually now would be the time to nail Soros before the ink on this decision dries.
Aside from the Constitution forbidding ex post facto laws we might be able to do that. What he MIGHT be caught on is if deeds done while this statute was locked up in the courts could be gone after.
Making it illegal to advocate open borders would violate 1A.
The law is against specific people taking specific action for a specific alien beneficiary.