Let California go with single payer if they want - but they MUST pay for it themselves.
That is the beauty of our Federal system. They can attempt things, with the approval of their own citizens, that are faster and more easily implemented than the Federal Government ever can.
That!
I am sure there is a way but what about military people and federal retirees both military and civilian that have their own federal health insurance. I don’t see how a state government can take those policies away.