So let me get this straight. You classify it as nullification when a bunch of Communists in one of Cali's most Leftist counties enact something which undermines US sovereignty? So by your logic, it would also be OK for said county to, for example, embrace Iran? Do I understand your (il)logic correctly?
Establishing treaties with foreign nations or providing support of foreign nations is a little different than ignoring federal law as it pertains to the internal affairs of a state or a county. One has a precedent that can be traced even to the Framers, one does not. Sorry you can't see the difference.