They aren’t laws.
They are regulations passed bu administrative agencies.
Those agencies report to POTUS and can be undone accordingly.
This is over before it starts. It might have to pass a few hurdles due to judge shopping.
Unfortunately, the enabling legislation by Congress for the EPA gives the agency's regulations the full force of law. Of course the executive branch can repeal regs but I am sure the courts will rule against Trump on lack of hearings and other procedural matters in repealing the CAFE. That is what the tyrannical black robed federal judges do.