An en banc federal appeals panel grilled lawyers on both sides of a case over a ruling earlier this year that many in the class action bar contended could threaten the viability of nationwide settlements.

The panel on Thursday reviewed a Jan. 23 decision in which the U.S. Court of Appeals for the Ninth Circuit de-certified a nationwide class action settlement with Hyundai Motor America Inc. and Kia Motors America Inc. after concluding that U.S. District Judge George Wu of the Central District of California had failed to analyze the consumer laws of several states. That so-called predominance analysis is required under Rule 23, the class action law under the Federal Rules of Civil Procedure, though many debate whether it’s as essential in the settlement context versus class certification.