Wyo. Stat. § 15-1-423: Municipal growth management agreements.

(a) Following a public hearing which may be held jointly between the affected cities or towns, any city or town may mutually agree with one (1) or more cities or towns defining the future geographical growth and expansion areas for each respective city or town. Any agreement under this section shall be reduced to writing and approved by the governing body of each city or town which is a party to the agreement. No agreement under this section shall be amended, terminated or voided by any party thereto after its execution except by the mutual written agreement of the parties to the agreement.

(b) Any agreement entered into by and between any cities or towns under this section shall provide that the parties to the agreement shall not annex real property located in any other party's defined growth and expansion area unless the nonannexing city or town's governing body consents, in writing, to any such annexation.

(c) Any agreement entered into by and between any cities or towns defining their respective future geographical growth and expansion areas prior to July 1, 2007 is hereby ratified and approved and may only be amended, terminated or voided by the mutual written agreement of the governing bodies of the parties thereto.

(d) Nothing in this section shall supercede other requirements for annexation under this article.