California et al. argue that Trump’s end run around the legislative branch’s exclusive authority to appropriate taxpayers’ money “violates the separation of powers doctrine.” But if so, it’s a violation that Congress itself seems to have authorized.

Can Congress do that? The nondelegation doctrine, a long moribund principle that prohibits one branch of government from passing off its responsibilities to another, suggests Congress cannot.

The Supreme Court has not invalidated an act of Congress as a violation of the nondelegation doctrine since the New Deal. But the justices recently heard a case that invites them to put some teeth into the rule, which historically has been invoked far more often than it has been enforced.