The Democrat-controlled U.S. House of Representatives moved late Thursday to defend the Affordable Care Act against an existential legal threat, tapping Munger Tolles & Olson LLP partner Donald B. Verrilli Jr. — who as U.S. solicitor general helped defeat another suit aimed at destroying the ACA — to represent them.

In a motion filed in Texas federal court, the House said it will join a newly launched appeal at the Fifth Circuit of a recent ruling that invalidated the ACA and has been stayed pending appellate review. Thursday’s motion also sought to intervene in undecided aspects of the case in district court, although those proceedings have been stayed and may be resolved by the appeal’s outcome.

Verrilli filed the motion along with other attorneys at Munger Tolles, which he joined in 2016, as well as lawyers with the House’s Office of General Counsel and the Constitutional Accountability Center.

The motion puts Verrilli in a familiar position. In 2012, as part of a historic case at the U.S. Supreme Court, Verrilli defended the ACA for the Obama administration against a constitutional challenge and prevailed in a 5-4 decision. In its motion, the House — which came under Democratic control on Thursday — said it would seek to intervene at the Fifth Circuit “as soon as a docket number exists that would permit it to do so.”

The case, which was filed by GOP state attorneys general, alleges the ACA’s individual mandate — previously upheld by the Supreme Court as a valid exercise of congressional taxing power — became unconstitutional when Republicans scrapped its tax penalty effective this year. U.S. District Judge Reed O’Connor last month agreed and subsequently invalidated the entire ACA, reasoning that it isn’t severable from the mandate, a key component of the law.

Through the U.S. Department of Justice, the Trump administration has declined to fully fight the GOP lawsuit, agreeing that the mandate is unconstitutional and that major parts of the ACA should also fall. As a result, nearly 20 Democratic state attorneys general have intervened to defend the law.

In Thursday’s motion, the House said the GOP state attorneys general and the Trump administration oppose its intervention, and that the Democratic state attorneys general “take no position with respect to this motion.”

The House on Thursday argued that “the intervenor states do not adequately represent” its interest. The House specifically noted the states “did not advance in their briefs in this court the argument that the plaintiff states or the individual plaintiffs lack standing to bring this action.”

In addition, the House said the Democratic-led states “may be unable to make a full-throated defense on the merits because doing so would undermine their claim to standing.” Verrilli could not immediately be reached for comment late Thursday.

The case is Texas et al. v. U.S. et al., case number 4:18-cv-00167, in the U.S. District Court for the Northern District of Texas.