The California Air Resources Board (CARB) has approved a set of emergency regulations to maintain certainty in the new-vehicle market after Congress revoked Clean Air Act waivers that supported the Low-NOx Omnibus and Advanced Clean Cars II standards.

The move is intended to prevent a situation where no clear emissions standards are in place, which could halt engine certifications and new-vehicle sales in California. According to CARB, this step responds to “unprecedented circumstances” that risk creating a regulatory gap in a program that has been in place for decades.

The amendments temporarily reinstate the previous LEV III standards, allowing manufacturers to choose between complying with those earlier requirements or the newer LEV IV and Omnibus standards. However, CARB warned that manufacturers who choose to follow only the older standards do so at their own risk if California’s legal challenge is ultimately successful.

The emergency rule will be submitted to the Office of Administrative Law (OAL) on September 22 and will be open for a five-day public comment period.

While the legal dispute plays out in court, California will continue certifying engines under both sets of rules to ensure the vehicle market keeps moving without disruption — and to make sure the state’s environmental goals remain on track.