Gay Marriage and the Rule of Law

On San Francisco Mayor Gavin Newsom's decision to issue marriage licenses in violation of state law, the Instaman writes:

Newsom would deny others the right to violate a law he believes in, but feels free to violate the law himself when he chooses, even though his sole claim to legitimacy as a government official comes from the law.

It's not civil disobedience when it's done by someone who controls the machinery of government -- it's usurpation, even when it's in a cause I agree with.

I'm inclined to agree.

But then I thought, what if this weren't gay marriage in the 2000s, but segregation in the 1950s? Would we feel the same way if the mayor of, say, Biloxi, Mississippi decreed that henceforth all Biloxi public facilities would be integrated, even though Mississippi state law called for them to remain segregated? Both issues involve equal protection. I'm not asking if either or both are 14th Amendment issues -- libertarians can and do disagree on that. I'm just asking whether either or both mayors are/would be doing the right thing in enforcing the idea of equal protection at the expense of the rule of law.

Merely asking the question. Not sure I know the answer.