15 U.S.C. § 260a : US Code - Section 260A: Advancement of time or changeover dates

    (a) Duration of period; State exemption
      During the period commencing at 2 o'clock antemeridian on the
    second Sunday of March of each year and ending at 2 o'clock
    antemeridian on the first Sunday of November of each year, the
    standard time of each zone established by sections 261 to 264 of
    this title, as modified by section 265 of this title, shall be
    advanced one hour and such time as so advanced shall for the
    purposes of such sections 261 to 264, as so modified, be the
    standard time of such zone during such period; however, (1) any
    State that lies entirely within one time zone may by law exempt
    itself from the provisions of this subsection providing for the
    advancement of time, but only if that law provides that the entire
    State (including all political subdivisions thereof) shall observe
    the standard time otherwise applicable during that period, and (2)
    any State with parts thereof in more than one time zone may by law
    exempt either the entire State as provided in (1) or may exempt the
    entire area of the State lying within any time zone.
    (b) State laws superseded
      It is hereby declared that it is the express intent of Congress
    by this section to supersede any and all laws of the States or
    political subdivisions thereof insofar as they may now or hereafter
    provide for advances in time or changeover dates different from
    those specified in this section.
    (c) Violations; enforcement
      For any violation of the provisions of this section the Secretary
    of Transportation or his duly authorized agent may apply to the
    district court of the United States for the district in which such
    violation occurs for the enforcement of this section; and such
    court shall have jurisdiction to enforce obedience thereto by writ
    of injunction or by other process, mandatory or otherwise,
    restraining against further violations of this section and
    enjoining obedience thereto.