By Tierney Sneed

What will the left’s legal resistance to a President Trump’s administration look like? A move Tuesday by two Obamacare enrollees seeking to intervene in an ongoing lawsuit targeting Affordable Care Act offers a preview.

The details of the lawsuit are wonky, but involve payments to insurers that if eliminated could bring immediate chaos to the individual health insurance market. The enrollees’ effort to get involved in the case also heralds the beginning of an era when Trump opponents — largely shut out from controlling other levers of power — will have to depend on the courts to push back on an agenda that they say is already raising serious legal and Constitutional concerns.

“This is the start of the Democrats’ major effort to scale back the Trump administration,” said Adam Winkler, a constitutional law professor at UCLA. “The courts are the only possibility for checking Donald Trump. With Republicans in control of Congress, we can’t expect to see Congress checking the President.”

Progressive legal advocates will be following a template used aggressively by conservatives in the Obama era who were able to block major agenda items with, in some cases, a single district court decision.

“It’s something that is in the Constitution,” said Elizabeth Wydra, the president of Constitutional Accountability Center, a public interest law firm which is representing House Democratic leaders in the Obamacare case. “We have a federalist system and while that’s something that has been perhaps more prominently embraced by the right, it’s definitely something that [the Constitutional Accountability Center] has long litigated progressive federalism positions.”

The case, House v. Burwell, was actually brought by congressional Republicans against President Obama’s administration — a rare move that was the culmination of a years-long conservative legal strategy to attack the ACA from any angle possible. Republicans in the lawsuit object to the administration’s use of the Treasury to fund payments to insurers that hadn’t been appropriated by Congress. The subsidies, known as cost-sharing reduction payments, help insurers keep out-of-pocket costs down for low-income consumers, as is required by the Affordable Care Act. The Obama administration has been fighting the lawsuit diligently, though it suffered a defeat when a federal court ruled in the House GOP’s favor in a decision blocking the payments that has since been appealed to the U.S. Court of Appeals for the D.C. Circuit.

Trump’s election has put a question mark over the lawsuit, especially after the House sought and was granted a delay in further proceedings until February so that the Trump administration and the GOP lawmakers can figure out their next steps. That’s where the new filing comes in.

The outside parties – the two Obamacare enrollees – are arguing that the Department of Justice won’t be able to be counted on to defend the payments once Trump takes office. They want to stand in defense of the payments rather than letting House Republicans and the Trump Justice Department negotiate the payments away without a fight.

“Until recently, Movants’ interests were aligned with the interests of the Executive Branch,” the filing said, noting the legal arguments the Obama administration had made in the case to continue to the payments.

“But the statements in the House’s recent motion indicate that the Executive Branch could well ‘change position after January 20, 2017, and enter into an agreement to dismiss the appeal or otherwise agree that the District Court’s injunction may take effect,” the filing said.

Health care experts have warned that stopping the payments would prompt major disruption in the individual marketplace. Since insurers would still be legally obligated under the ACA to keep out-of-pocket costs low — but without the federal subsides promised to help them to do so — they may either hike premiums significantly to make up the shortfall or exit the individual marketplace entirely.

“Recipients of the cost-sharing reductions who purchased health care insurance policies for 2017 will likely face early termination of those policies, because the federal government permits insurers to leave the exchanges in the event cost-sharing reimbursement payments cease,” the filing said.

But beyond the policy implications of eliminating the payments, the motion to intervene is also focused on how Trump and House Republicans go about ending the payments. A footnote explains that the enrollees don’t dispute the ability of Congress and the President to pass a law changing the ACA, or even the Trump administration’s ability to change its legal interpretation of the payments (though that might also invite a lawsuit).

“In each of those cases, Congress and the president are making the decision based on their Constitutional power, it will be clear where the responsibility lies and they can be held accountable by people who like or don’t like the decision,” Andrew Pincus, a Washington, D.C., lawyer representing the enrollees, told TPM. “What would be improper to do is the courts to impose the decision on this issue in a case in which both sides agree, because that it will look like the courts are requiring a decision.”

For this and other reasons, the case is being watched by legal advocates outside the health care policy world. The direction that the Department of Justice takes in this case after Trump takes office next month could provide a hint of how his DOJ will operate on various other issues where it will be called upon to defend federal laws — including laws that Trump and his administration officials disagree with on a policy level.

“The motion filed in this case reflects concern that the next administration may seek to abandon defending federal laws,” said Kristen Clarke, president and executive director of Lawyers’ Committee for Civil Rights. “The civil rights field in particular has concerns that there may be changes in the Justice Department position, or stances that run contrary to the longstanding position taken by the Justice Department in important cases.”

In its request to delay the case until Trump was inaugurated, the House GOP said there was “least a significant possibility of a meaningful change in policy” with regards to the payments, that could allow them to agree to withdraw or settle the case.

“The intervention motion shows that there are people who have life or death interests in the cost-sharing reduction payments,” Wydra said. “If they are going to be denied the benefits of that program, then the denial of those benefits needs to go through the standard political processes or have a court declare them invalid. But to simply have a backroom deal that is going to cut out the important benefits for the people who depend on them is not the way that it should be done.”