The Trump Administration has announced plans to end a special waiver that currently allows California to regulate vehicle emissions differently than what the federal government mandates.

The change could affect the state’s Red Sticker/Green Sticker program that is used to regulate the operation of off-highway motorcycles.

Reports from news services Bloomberg and Reuters said that ending the waiver would eliminate California’s stricter vehicle-emissions standards. The reports also stated that the move would cap federal fuel economy requirements at 35 mpg, rather than allowing them to rise to 50 mpg by 2025.

Thirteen states and the District of Columbia have adopted California’s stricter emissions standards. Taken together, this adoption accounts for nearly 40 percent of U.S. car and truck sales. (Motorcycles are not included in this percentage.)