42 USC 8522 - Out-of-State vehicles to be exempted from odd-even motor fuel purchase restrictions

(a) General rule 
Notwithstanding any provision of any Federal, State, or local law, any odd-even fuel purchase plan in effect in any State may not prohibit the sale of motor fuel to any person for use in a vehicle bearing a license plate issued by any authority other than that State or a State contiguous to that State.
(b) “Odd-even fuel purchase plan” defined 
For purposes of this section the term odd-even fuel purchase plan means any motor fuel sales restriction under which a person may purchase motor fuel for use in any vehicle only on days (or other periods of time) determined on the basis of a number or letter appearing on the license plate of that vehicle (or on any similar basis).