Idaho Code § 30-801: Contracts for municipal water supply.

No corporation formed to supply any city or town with water must do so unless previously authorized by an ordinance of the authorities thereof, or unless it is done in conformity with a contract entered into between the city or town and the corporation. Contracts so made are valid and binding in law, but an exclusive right must not be granted. No contract or grant must be made for a term exceeding fifty (50) years.