(a)Restriction on Requirements.—
No State, political subdivision of a State, interstate agency, or other political agency of two or more States may enact or enforce any law, rule, regulation standard, or other provision having the force and effect of law that requires a motor carrier, motor private carrier, freight forwarder, or leasing company to display any form of identification on or in a commercial motor vehicle (as defined in section 14504a), other than forms of identification required by the Secretary of Transportation under section 390.21 of title 49, Code of Federal Regulations.
(b)Exception.—Notwithstanding subsection (a), a State may continue to require display of credentials that are required—
under the International Registration Plan under section 31704;
in connection with Federal requirements for hazardous materials transportation under section 5103; or