Please don’t declare a national emergency

With Democrats in Congress refusing to appropriate $5.7 billion for a border wall, President Donald Trump now says he may declare a national emergency. He’s probably right that he has the legal authority, but it would set a bad precedent that conservatives who believe in the separation of powers could live to regret.

Mr. Trump may declare an emergency that would let him reallocate funds that Congress has appropriated for military construction to build his wall. He’s warned that if negotiations with Democrats don’t “work out, probably I will do it. I would almost say definitely.”

An emergency declaration could let Mr. Trump end the shutdown without conceding an inch to House Speaker Nancy Pelosi, but it would strain the limits of his executive authority.

Presidents over the decades have invoked emergency powers, sometimes grounded in law though often not. While a president may sometimes need to act with dispatch, abuses of executive power prompted Congress to pass the National Emergencies Act of 1976. The law requires the president to activate his powers under one of 130 or so statutes that authorize executive emergency actions.

Members of Congress with a two-thirds vote may revoke an emergency declaration, but the president otherwise enjoys wide latitude within his statutorily delegated powers.

Republicans rightly criticized Barack Obama for governing by fiat. While Mr. Trump might be on sounder legal footing than Mr. Obama was when he legalized millions of undocumented immigrants, Mr. Trump still would be spending scarce military funds essentially to fulfill a campaign promise.

The left’s hyperbolic warnings about an imperial Trump presidency haven’t borne out, and his administration’s uses of executive power have for the most part been restrained and legally careful. A political spending fight over the wall doesn’t warrant a national-emergency raid on military funds.