It does seem like a good case could be made that states setting their own requirements on automobiles can place an undue burden on interstate commerce.
States forming a compact to restrict development of resources, to manipulate other states energy policy by threat of court challenges, lawsuits over emissions which quite often originate out of country (ozone from Asia); but, are carried by the wind across a state’s border ... address these issues also.
Don’t forget northern Alberta. The DEF systems are complete crap and do nothing but shorten your engine life. It freezes up and puts your truck in limp mode. I deleted my HD 3500 when she was still brand new, put in a small Congnito 4 inch lift and called it good. Now she’s at 237,000kms and I have drove the roughest stuff we have available. Cooper MTs and regular maintenance. Screw california’s regs.