(a) Except as provided in paragraph (a)(2) of this section, these regulations preempt any State or local law, rule, regulation, or order to the extent that:
(1) Compliance with both the State or local requirement and this subpart is not possible; or
(2) Compliance with the State or local requirement is an obstacle to the accomplishment and execution of any requirement in this subpart.
(b) The alcohol testing requirements of this title shall not be construed to preempt provisions of State criminal law that impose sanctions for reckless conduct leading to actual loss of life, injury, or damage to property, whether the provisions apply specifically to transportation employees or employers or to the general public.
ACE rules page: Part 120 in plain English