President Donald Trump revoked California’s nation-leading electric vehicle sales rules in a White House ceremony last week, following through on his Day 1 executive order to roll back EV mandates. California officials are now scrambling to find alternatives to clean the state’s air — and avoid federal sanctions.

Trump also revoked two other Biden-era waivers on Thursday. Those would have allowed California to require vehicle makers to produce an increasing number of zero-emission heavy-duty trucks, and to reduce nitrogen oxides, a component of smog, from heavy-duty highway and off-road vehicles and engines.

Regulations would have required at least 100% of new vehicles sold in the state by 2035 be electric or plug-in hybrids