No it doesn't. Every American has a duty to ignore unconstitutional laws.
Yes, and a duty to vote to acquit. Their laws become meaningless unenforceable junk if juries refuse to convict.
I guess that’s all fine and dandy and you can do your duty behind bars. 55 mile an hr speed limit may be unconstitutional as well but drive 105mph and see what happens!
Probably not a constitutional issue, but one of employment law. As a condition of employment, he no doubt was required to adhere to rules that he was fully aware of, and certainly he had knowledge of the gun restriction.