In Florida House of Representatives v. Hon. Charles Crist, the Florida Supreme Court exercised original jurisdiction (writ of quo waranto) to hold that the Governor's approval of a gambling compact with various tribes was outside his constitutional authority because the compact permitted violations of state law.
The Court held that even under the apparent federal authority, the gambling permitted bythe compact was prohibitted by legislation, and the governor therefore had no power to enter such a compact. The Court did not reach the question of whether or when the Governor could sign a compact that did not otherwise directly violate state law; or whether such a compact would have to be ratified first.
On one hand, this is a fairly bread and butter separation of powers case. On the other, it demonstrates that we all need to become way more familiar with the writ of quo waranto - I suspect that we will be seeing it more often as a way to challenge the authority of executive actors to take certain actions (as beyond their delegated authority, when the APA doesn't control it), and perhaps against local governments to prevent actions that violate state law.