If a single citizen in that town is harmed by one of those illegals, the Chief will be liable in more ways than one.
The Trump administration could seize on your idea by promising DoJ legal action to support the family of anyone who was injured by an illegal where the local/state law enforcement deliberately frustrated federal efforts. Just as most J6 defendants plead guilty because of the expense of fighting the FedGov purse, so too would locals likely settle to save the expense involved fighting against an adversary with unlimited funds.
Hmmm. Someone dying because of overdose should be included in that scenario.
The dimorats do seem to be very fond of their narcotics and willing to fight to keep the drugs flowing.. If we can somehow manage to get the cartel out and drive the cost of drugs up just maybe things will improve somewhat...maybe.