49 CFR 174.2 – Limitation on actions by states, local governments, and Indian tribes
Sections 5125 and 20106 of Title 49, United States Code, limit the authority of states, political subdivisions of states, and Indian tribes to impose requirements on the transportation of hazardous materials in commerce. A state, local, or Indian tribe requirement on the transportation of hazardous materials by rail may be preempted under either 49 U.S.C. § 5125 or 20106, or both.
(a) Section 171.1(f) of this subchapter describes the circumstances under which 49 U.S.C. § 5125 preempts a requirement of a state, political subdivision of a state, or Indian tribe.
(b) Under the Federal Railroad Safety Act (49 U.S.C. § 20106), administered by the Federal Railroad Administration (see 49 CFR parts 200 through 244), laws, regulations and orders related to railroad safety, including security, shall be nationally uniform to the extent practicable. A state may adopt, or continue in force, a law, regulation, or order covering the same subject matter as a DOT regulation or order applicable to railroad safety and security (including the requirements in this subpart) only when an additional or more stringent state law, regulation, or order is necessary to eliminate or reduce an essentially local safety or security hazard; is not incompatible with a law, regulation, or order of the United States Government; and does not unreasonably burden interstate commerce.