And so, in a breathtaking display of executive disregard for the separation of powers, the White House is thumbing its nose at Congress, the Constitution and the will of the American people, the majority of whom oppose a border wall.

Even as he spun this as an act of strong leadership, Mr. Trump acknowledged that his declaration resolves nothing and creates a host of legal, legislative and political troubles. He predicted that the move would prompt swift legal pushback, which it did. Less than four hours after the announcement, a government watchdog group filed suit, demanding that the Department of Justice hand over “documents concerning the legal authority of the president to invoke emergency powers.” Soon after, the State of California announced its intention to sue. On Thursday, even before the announcement, Protect Democracy and the Niskanen Center announced plans to file on behalf of El Paso County and the Border Network for Human Rights. So the floodgates are open.

Mr. Trump predicted that he would lose the first couple of court rounds, particularly in California federal courts, but would ultimately be vindicated by the Supreme Court. Critics of the move expect things to turn out differently. Whatever the outcome, the legal issues are complex, and the case could wind up bogged down indefinitely, meaning not much wall for now.

Moving from the legal to the political realm, Republican lawmakers will very likely find themselves in a pickle. Congress has the power to override a national emergency declaration by passing a joint resolution. To prevent opponents from stalling the bill indefinitely, once one chamber passes the resolution, the other must hold a vote on it within 18 calendar days. House Democrats have already announced their intention to hold such a vote, and are expected to prevail. This will then put Senate Republicans in the position of having to vote on whether to support a presidential grab of Congress’s power.

To survive a presidential veto, such a measure would need to pass with two thirds of the votes i n both chambers — which seems unlikely. But the vote itself will prove awkward for Republicans, forcing them to go on record as to whether they have officially abandoned their constitutional duties.