Why should he have to do it?

White House press secretary Karine Jean-Pierre offered a stunning defense Wednesday of President Biden’s refusal for more than three years to use executive powers to tackle the US-Mexico border crisis — after a reporter asked, “Why isn’t he doing anything?”

“Why should he have to do it unilaterally?” Jean-Pierre replied — justifying Biden’s prior inaction as he considers finally using his presidential powers to limit the number of asylum applicants allowed into the US after illegally entering the country.

The 81-year-old president’s top spokeswoman added: “Why shouldn’t we do it in a legislative way?”

The defense was immediately ridiculed online, with former President Donald Trump’s longtime adviser Jason Miller tweeting, “3-D chess from KJP right here.”

“No chance [fellow White House spokesman John] Kirby would have been smart enough to shift the blame to others and act as though Joe Biden wasn’t the sitting President of the United States,” Miller added, making light of reported tension between Kirby and Jean-Pierre.

“This is why KJP will remain in place as Press Secretary!”

Biden is considering issuing an executive order to shut down the US-Mexico border if migrant crossings surpass 4,000 per day, sources have told The Post — though Jean-Pierre didn’t reply to a shouted question Wednesday about the status of that pending action.

A failed congressional border policy package would have also granted Biden that authority, but Republican opponents say Biden already had that power and administration lawyers now apparently agree, though the precise timing remains unclear.

The border crisis exploded in 2021, during Biden’s first year in office, as he used executive powers to unilaterally end Trump’s “Remain in Mexico” policy, which required most asylum seekers to remain south of the border as US immigration courts reviewed their claims of persecution.

Biden also halted construction of Trump’s US-Mexico border wall, proposed amnesty for most illegal immigrants already in America, and began allowing a majority of people who illegally crossed the border into the interior — providing them government-issued smartphones and paperwork that entitles them to work permits following an initial six-month wait period.

Backlogged court proceedings mean that some migrants with dubious asylum claims could remain in the US with work authorization for many years — with appointments for a preliminary pre-court check-in “fully booked” in New York City through late 2032 at one point last year

That initial appointment would be followed by additional years of delays before an actual decision is made.

The surge in migrants has burdened state and local governments, including in New York City, where municipal services have been slashed to help finance food and housing for recent arrivals.

Biden’s possible executive order clamping down on the border would come as polls show that immigration is one of his biggest liabilities ahead of his Nov. 5 rematch against Trump.

A record 2.5 million illegal immigrants were apprehended after crossing the southern border in fiscal year 2023, which ended Sept. 30, followed by an all-time monthly record of nearly 302,000 in December.

Homeland Security Secretary Alejandro Mayorkas, who was impeached in February by House Republicans for allegedly failing to secure the border, said in January that more than 85% of those detained for illegally crossing the border were being released into the US.