Lawyers on both sides of a high-profile case against Hyundai, citing a circuit split, have asked an en banc appeals panel to upend a ruling that they say threatens the future of nationwide class action settlements.

In dual petitions for rehearing filed on Thursday before the U.S. Court of Appeals for the Ninth Circuit, plaintiffs attorneys and lawyers for defendants Hyundai Motor America and Kia Motors America Inc. both argued that an en banc panel should review a Jan. 23 decision that conflicts with the Third Circuit, and its own precedent. The 2-1 decision, which decertified the nationwide class in their settlement, also is contrary to the U.S. Supreme Court’s 1997 decision in Amchem Products v. Windsor, they wrote.