The Supreme Court's decisions are always final unless they agree to rehear a case, which rarely happens. The Supreme Court is the final authority on federal and constitutional law in the United...
A Supreme Court decision is only irrelevant in two ways. The first is "de facto". This is when a decision is obviated by the fact that it no longer has any practical meaning. For instance, let's...
The President (Executive Branch) is ultimately responsible for ensuring Supreme Court decisions are enforced. The Supreme Court has no enforcement power of its own.