Yes, there are multiple ways a state can phase out sales of new gas vehicles, or take measures that will have that effect. Certain states have a clearer path than others.
California is specifically authorized by the federal Clean Air Act to impose more stringent standards on vehicle emissions than federal standards. Using this authorization, California has imposed standards for Zero Emissions Vehicles, or ZEVs. Its ZEV mandate sets up a credit system relating to a requirement that a certain percent of passenger vehicle sales by each automaker be ZEVs. The ZEV mandate aims for 1 million EVs in California by 2020, 1.5 million by 2025, and 4.3 million by 2030. (See the 2016 ZEV Action Plan.)
Under this authorization, California could require that 100% of vehicles sold after a certain date be ZEVs.
Other states may administer California’s ZEV requirements under Section 177 of the Clean Air Act. Currently the “Section 177 ZEV States” that have opted to follow California’s ZEV mandate are Connecticut, Massachusetts, Oregon, Maine, New Jersey, Rhode Island, Maryland, New York and Vermont.
California’s ZEV mandate must be approved via a waiver by the federal Environmental Protection Agency (EPA), and the EPA must grant the waiver if certain criteria are met. The EPA has already approved a California mandate that requires a certain percent of vehicles sold be ZEVs (via a credit system) for each year beginning 2018 as follows:
If California wishes to change the current mandate it must seek a new waiver from the EPA to do so, which the EPA is required to grant if certain conditions are met. Under the current administration, there is concern the EPA would not grant a waiver, despite the lack of any legal basis for a denial; therefore, California may choose to wait until a new administration is in place before making changes to the current mandate.
In addition to following the California ZEV mandate, there are other ways California and other states could effectively phase out sales of new gas/diesel vehicles by a date certain. States control vehicle registration and vehicle use fees, vehicle sales taxes and gas taxes. Accordingly, a state could take measures to reduce sales of gas/diesel vehicles such as prohibiting registration of such vehicles after a certain date, or imposing steep vehicle registration fees or gasoline taxes.