Except that the Supreme Court does have a say over whether or not the Supreme Court has a say over a state choosing to ban gambling.

I do agree that prediction markets are BS gambling pretending to be something else.

But factually, SCOTUS does have authority over the application of the supremacy clause.

What is the Supremacy Clause?

What is stare decisis?

An invented doctrine not codified anywhere in written law.

Which decision is applicable?

The case would be on CFTC authority vs state authority.

You’d be hard pressed to argue that states should be individually able to control futures trading

You’d be similarly hard pressed to read the CFTC magicking gambling authority as anything but a major question.