“I didn’t need to do this,” President Trump insisted at a Rose Garden appearance on Friday, as he declared a national emergency aimed at shaking loose a few billion dollars in financing for his beloved border wall.

The president’s assertion was both ludicrous and self-defeating. If a declaration was unnecessary and the wall on track (the wall is “very very on its way,” the president said earlier in the week), how could he claim to be addressing an emergency? As Mr. Trump explained it, “But I’d rather do it much faster.” A presidential desire for speed does not constitute a crisis — no matter how eager a president is to camouflage his failures.

In reality, the wall is not a done deal, and Mr. Trump has spent the past few months — the past two years, really — failing to convince either Congress or Mexico to pay for it. This week’s bipartisan spending bill, which contained no more wall money than the one over which Mr. Trump shut down the government in December, was a particularly humiliating defeat.

Desperate to save face, the president and his team cooked up a nonemergency emergency with the aim of seizing funds already appropriated for other purposes. Currently, the plan is to pull $2.5 billion from the military’s drug interdiction program, $3.6 billion from its construction budget and $600 million from the Treasury Department’s drug forfeiture fund. The White House plans to “backfill” the money it is taking from the Pentagon in future budgets.

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.