Answer:
A) Intergovernmental immunity.
Step-by-step explanation:
This case is very similar to a Supreme Court case Breard v. Alexandria, 341 U.S. 622 (1951).
In that case, the appellant was a private company, and the Supreme Court ruled that the ordinance did not violate the Due Process Clause, the Commerce Clause or Freedom of Speech.
So the employee's only defense it to appeal to intergovernmental immunity. This doctrine prohibits state and local governments from interfering with federal actions.