N.D. Cent. Code § 40-33.3-04

The agreement may be amended at any meeting of the representatives of the member cities for which notice, stating the purpose, is given to each representative of each member city and unless the agreement provides otherwise, is effective when ratified by resolutions of the governing bodies of a majority of the member cities and approved by a majority of the qualified electors voting on the question at any regular or special election in each of those member cities constituting the majority. Each amendment and the resolutions of the governing bodies approving it shall be filed for record with the secretary of state.