Among the many unintended legacies of Barack Obama, one has gone largely unnoticed: the emergence of a novel form of resistance to executive overreach, a check-and-balance improvised in reaction to his various presidential power grabs.

It’s the revolt of the state attorneys general, banding together to sue and curb the executive. And it has outlived Obama.

Normally one would expect Congress to be the instrument of resistance to presidential trespass. But Congress has been supine. The Democrats in particular, approving of Obama’s policy preferences, allowed him free rein over Congress’ constitutional prerogatives.

Into that vacuum stepped the states. Florida and 12 others filed suit against Obamacare the day it was signed. They were later joined by 13 others, making their challenge the first in which a majority of states banded together to try to stop anything.

They did not always succeed, but they succeeded a lot. They got Obamacare’s forced Medicaid expansion struck down, though Obamacare as a whole was upheld. Later, a majority of states secured stays for two egregious EPA measures. One had given the feds sovereignty over the generation and distribution of electricity (the Clean Power Plan), the other over practically every ditch and pond in America (the Waters of the United States rule).

Their most notable success was blocking Obama’s executive order that essentially would have legalized four million illegal immigrants. “If Congress will not do their job, at least we can do ours,” said Obama. Not your job, said the courts.

Democrats noticed. And now with a Republican in the White House, they’ve adopted the technique. Having lost control of Congress, they realize that one way to curb presidential power is to go through the states. They just did on Trump’s immigration ban. Taking advantage of the courts’ increased willingness to grant “standing” to the states, Washington state and Minnesota got a district court to issue an injunction against Trump’s executive order and got it upheld by the 9th Circuit. Where the ban died.

A singular victory. Democratic-run states will be emboldened to join together in opposing Trump administration measures issuing from both the agency rulings (especially EPA and the Department of Education) and presidential executive orders.

Is this a good thing? Regardless of your party or policy preferences, you must admit we are witnessing a remarkable phenomenon: the organic response of a constitutional system in which the traditional barriers to overreach have atrophied and a new check-and-balance emerges almost ex nihilo.

Congress has allowed itself to become an increasingly subordinate branch. Look at how reluctant Congress has been to even consider a new authorization for the use of force abroad, an area in which, constitutionally, it should be dominant. Look at today’s GOP Congress, having had years to prepare to govern, now appearing so tentative, almost paralyzed. “Many Republican members,” reports The Washington Post, “are eager for Trump to provide clear marching orders.” The president orders, Congress marches — that is not how the Founders drew it up.

Hence the state attorneys general rise to check the president and his functionaries. This is good.

Not because it necessarily produces the best policy outcomes. It often doesn’t.

Not because judicial grants of standing are always correct. The 9th Circuit, in effect, granted Minnesota and Washington standing to represent the due process rights of Yemeni nationals who’ve never set foot in the United States — an imaginary harm to states that presupposes imaginary rights for Yemenis.

And not because it’s necessarily good for the judicial system to acquire, through this process, yet more power. This really should be adjudicated by the elected branches. Problem is: Congress has abdicated.

Nonetheless, the revolt of the AGs is to be celebrated. It is a reassuring sign of the creativity and suppleness of the American Constitution, of its amphibian capacity to grow a new limb when an old one atrophies.

This is, of course, not the first time the states have asserted themselves against federal power. There was Fort Sumter, 1861, when the instruments employed were rather more blunt than the multistate lawsuit. All the more reason to celebrate this modern device.

I’m sure conservatives won’t like many of the outcomes over the next four years, just as many liberals deeply disapproved of the Obama-blocking outcomes of the recent past.

The point, however, is not outcome but process. Remarkably, we have spontaneously developed a new one — to counter executive willfulness. There’s a reason that after two and a half centuries the French are on their Fifth Republic and we are still on our first.

© 2017, The Washington Post Writers Group