N.D. Cent. Code § 40-33.3-01

Any two or more cities each of which is over forty thousand population may form a municipal pipeline authority by executing an agreement authorized by a resolution of the governing body of each city and approved by not less than a majority of the qualified electors voting on the question at any regular or special election in each of those cities. Any city may become a member of an existing municipal pipeline authority, without regard to population, upon executing an agreement with the authority.