Wyo. Stat. § 41-9-305: Hearing.

Upon the day fixed for the hearing on such petition, all parties owning lands, or any interest or easement in land, within said district, proposed to be divided, or whomsoever would be affected thereby, or the commissioners of the original district, may appear and contest the granting of said petition on the grounds that said proposed division will not serve the best interests of all parties interested, and the grounds specified in W.S. 41-9-111.