HERE’S HOW the United States government works, according to the Constitution: Congress debates various priorities and chooses how much to spend on each. The president either vetoes the appropriations bill or signs it. If he signs it, he and his subordinates use the funds as Congress instructed.

This is not how things have been proceeding in the matter of President Trump’s pet anti-migrant project — a wall along the U.S.-Mexico border. Congress, by large bipartisan majorities, has voted for spending bills including far less wall money than Mr. Trump wants, and he has raided a military construction account to get the dollars, spuriously citing “emergency” authority from other statutes. Mr. Trump got his hands on $3.6 billion in this manner during 2019, after failing, despite forcing a 35-day government shutdown roughly a year ago, to persuade Congress to supply $5.7 billion. Mr. Trump also rerouted $2.5 billion from a Defense Department counternarcotics fund and $600 million in Treasury Department funds, under slightly more plausible legal grounds.

Now, The Post’s Nick Miroff reports that Mr. Trump plans to repeat this constitutionally dubious gambit in the current fiscal year, except diverting a slightly larger quantity of military construction funding — $3.7 billion. Counternarcotics and Treasury money will also be tapped. This, despite the fact that Congress once again, in a spending bill Mr. Trump signed Dec. 20, limited border-barrier funding to $1.375 billion.

The statute Mr. Trump is invoking was clearly intended to enable a president to redirect money among various military purposes in time of war or other security crisis, not to construct a permanent structure in response to a chronic issue in the civilian world such as cross-border migration and drug smuggling — even on the unlikely assumption that a wall would be effective against those. Opponents, including the Democratic-majority House, have sued to stop the president from redirecting the funds, but both the Supreme Court and the New Orleans-based federal appeals court have permitted the wall construction to proceed, at least for now.

Congress has options other than the courts. Federal law permits lawmakers to override Mr. Trump’s emergency declaration, though effectively it would take a two-thirds majority of both houses to do it, because a presidential veto would have to be overcome. Last year, the House mustered 245 votes to cancel the emergency; the Senate got all the way to 59 votes, 12 of them Republican. But Mr. Trump vetoed the legislation, and the two chambers failed to override his action.

If Mr. Trump proceeds again this year, House Speaker Nancy Pelosi (D-Calif.) should try again. At a minimum, it would force Senate Majority Leader Mitch McConnell (R-Ky.), and his fellow Republicans, to go on the record again, because under the law the upper chamber is required to vote on this particular resolution. Mr. McConnell and most of his caucus in the end acted consistent with fealty to Mr. Trump, not the constitutional prerogatives of the independent legislative branch. They, and House Republicans, should be given a chance to mend their ways — or to persist in them, with full accountability before the public.

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