What's the legal term of art for "conventional wisdom"?

For the past few days I've been trying to recall a particular legal term of art, so I'm fishing here to see if anyone can remind me.

What's it called when there's a law that everyone ignores, or has ignored for a very long time, and nobody cares if the law is violated so it's not enforced, to the point where the law is deemed invalid? It's not conventional wisdom or general acceptance or well, that's just how it is. It's not just a law that's still on the books but isn't enforced. I mean a law that is still on the books but if you're prosecuted or sued, you'd win in court.

The example I'm thinking of is the general acceptance that Senator McCain is citizen enough to run for president. (I'm not asserting that he's ineligible on this -- or any -- basis. I'm using the situation merely as an example. And to prove that, I'm not using the "election" tag for this post.) The deal is that there has been a question as to whether he's a "natural born citizen" because he was born in the Panama Canal Zone, at a time when people born in the Canal Zone were not considered natural born citizens. But he's been a Senator since the 1980s and no one has proposed (seriously) that he is constitutionally disqualified because of the circumstances of his birth. And actually, to tell the truth, I think this question is totally moot, because since the mid-1950s, if you were born in the Canal Zone after February 1904 and at least one of your parents is a citizen, you're "declared to be a citizen." The only question left is whether citizen in Title VIII there is equivalent to the constitutional language of natural born citizen. I'm sure there's caselaw about that, and I'd bet that the terms are one and the same. This is a 10-minute blog post, not a law review Note, so I'm leaving it at a bet. Basically I'm wondering what you call it, if there is no caselaw about it, or if the statute hadn't been passed in the 1950s, when people would just say, "Well, this person was born in the Canal Zone in the 1930s, and we owned the Canal Zone at that time, so he's a constitutionally enough a citizen."

What's the term for that?