The courts slam the brakes, saying the president's creative reimagining is just plain illegal. It happened again this week — with an exclamation point — when two federal courts invalidated the central plank of Trump’s economic agenda: a slate of emergency tariffs that spurred uncertainty across the globe.

For all the White House’s histrionics about a “ judicial coup ” against President Donald Trump’s agenda, the judiciary until Wednesday had only trimmed his policies.

Reordering the global economy by executive fiat was an unconstitutional end-run around Congress’ powers, the three-judge panel of Trump, Obama and Reagan appointees ruled in a scathing rebuke of Trum...