Marbury v Madison has always been, in one sense, hanging out there in midair like Wile E. Coyote over a canyon. In another sense, it mirrors what just about every other country with a binding constitution does: treat findings that an Act or an exercise of power is unconstitutional as an enforceable finding of ultra vires, rather than a simple declaratory remedy. (This means almost everybody except the UK, at least in the West. Even the UK had constraints of this sort when it was in the EU.)

There are two really messy prospects for the US right now. The first is that the Roberts Court will suddenly reverse its States Rights and pro-Congress biases and back the administration by allowing exercises of executive power that were previously though to be beyond the pale; the second is that the courts will curb the administration and that it will ignore the courts. In either case it will lead to a likely increase in the likelihood of people deciding to take the law into their own hands, on the grounds that they cannot rely on the courts. And that is the precondition for a civil war.