Nearly six years after defending the Affordable Care Act at the Supreme Court, former U.S. Solicitor General Don Verrilli is diving back into the fight to defend the Obama-era law.

Verrilli is among a team of lawyers representing the newly Democratic-controlled House of Representatives, which sought late Thursday to step in as a defendant in a lawsuit threatening to dismantle the ACA. Texas Attorney General Ken Paxton and several other states are leading that challenge.

The House, backed by Verrilli and their newly-hired counsel Douglas Letter, filed a motion to intervene in the lawsuit in Texas. It is one of the first major acts for Democratic lawmakers who stepped into the House majority earlier Thursday and repeatedly vowed to step in to defend the health care law.

The filing also represents the first big move on the job for Letter, a 40-year veteran of the Justice Department's Civil Appellate staff who left his post at the Georgetown Law Center in late December 2018 to join the House as its top counsel.

Verrilli, now a partner at Munger, Tolles & Olson, isn't stepping into entirely new territory: He successfully defended the health care law in the Supreme Court's landmark 2012 case NFIB v. Sebelius.

Judge Reed O'Connor of the U.S. District Court for the Northern District of Texas ruled in December that a congressional tax law passed in 2017—which zeroed out the penalty imposed by the ACA's individual mandate—rendered the entire health care law unconstitutional.

The law, however, remains in effect while the ruling is being appealed to the U.S. Court of Appeals for the Fifth Circuit. A coalition of states, led by California Attorney General Xavier Becerra, have defended the law after the Justice Department made the controversial decision to drop its defense. Those states filed a notice of appeal Thursday.

Verrilli and Letter assert that the Justice Department's move opened the door for lawmakers' intervention. They wrote: “[F]ederal law provides that the Attorney General has a right to intervene in litigation to defend the constitutionality of an Act of Congress when the United States or one of its agencies or officers is not already a party, and it empowers the House and/or the Senate to intervene to defend a statute if the Attorney General fails to do so.”

At the very least, they contend, their defense would address the same legal questions being litigated in the case, and their participation would cause “no undue delay or prejudice to the Court or the parties.”

The conservative states first brought their legal challenge to the ACA in February.

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