"California's refusing to register 80,000 older trucks because they don't have particulate filters. At the same time, they've declared that all new commercial trucks must be fully electric by 2035, and all current trucks must have filters by 2023. Of course, no fully electric trucks exist currently, and you can't add filters to existing engines—you have to install a new engine designed from the beginning to work with the filters. Faced with exorbitant costs that can't be recouped within these timelines, many truckers simply aren't operating in California any longer, thus there aren't enough "clean" trucks to move shipments from the ports."

https://www.freightwaves.com/news/new-california-environmental-law-puts-thousands-of-truck-registrations-on-hold