The President swears to uphold the Constitution, but what if he chooses not to?

As you point out, the worst that happens is the court eventually overrules, but often the damage has already been done and the President can just try again in a slightly modified way.

Is such disregard for the Constitution treason?

At the very least it is an impeachable offense, but only if congress has the will to impeach.

So that chick in Babel expected no one to look at her hairy monster?