President Joe Biden doesn’t have the power to shut down the border. Except when he decides that he does.

Earlier this year, Biden vowed to “shut down” the border if only Congress would give him the legislative high sign.

“Just give me the power. I’ve asked from the very day I got into office,” he said in January. “Give me the Border Patrol, give me the people, the judges — give me the people who can stop this and make it work right.”

Turns out he was “the people.”

The president is planning executive action that would allow him to shut down the US-Mexico border once the number of migrant crossings reaches 4,000 per day, a source close to the White House told The New York Post Wednesday.

It matches a provision in February’s failed Senate bipartisan border bill, which gave the president authority to expel migrants when border crossings reached that number.

It’s an odd number to set as a basis for action, as the U.S. has surpassed that number for months. In March, southwestern border authorities stopped an average of more than 6,300 migrants per day — and that doesn’t include so-called “gotaways” who escaped detection and arrest.

At the end of last year, Border Patrol processed nearly 50,000 migrants who entered the U.S. illegally in a five-day span, with daily apprehensions surpassing 10,000 three times, up from the 6,400 average in November, according to federal data obtained by CBS News.

We’ve hit 4,000 a day, many times. So why that number now? Does this baseline mean that action will be immediate? And how effective will Biden’s actions be?

As illegal immigrants make the headlines after committing crimes, sometimes violent, sometimes drug-related, some have turned out to be repeat offenders. The crossed the border, got caught and arrested, and deported. But then they re-enter illegally. Sometimes they’re caught and jailed, but the strained Border Patrol can only do so much.

Using 4,000 crossings a day as the basis for “shutting down the border” is looking at the wrong number. What Biden should have been doing all along is looking at the costs to cities, towns and states tasked with housing and caring for migrants.

Mayors and governors around the country have been scrambling for months to find the money to cover shelter for the migrant influx, with little to no help from the feds. That was the canary in the coal mine.

Services are facing cuts as budgets burst at the seams to pay for  migrant care. If Biden had taken action back in January, when he insisted he didn’t have the power to do what he’s reportedly going to do now, it would have made some difference.

But since Biden has rediscovered his Executive Order powers, he shouldn’t let up. Open the fed coffers to help states like Massachusetts defray the cost of the migrant influx.

Of course this election-year grandstanding. But as long as Massachusetts starts getting some big checks with a D.C. postmark, that’s fine with us.

Editorial cartoon by Joe Heller (Joe Heller)