Idaho Code § 43-101
Whenever fifty (50), or a majority, of the holders of title, or evidence of title, to lands susceptible of one or more modes of irrigation from the same or different sources and by the same or different systems of works, desire to provide for the irrigation of the same, or when for other reasons they desire to organize the proposed territory into one district, they may propose the organization of an irrigation district under this title: provided, said formation into one (1) district meets with the approval of fifty (50), or a majority of the holders of title, or evidence of title, to lands in each of the communities affected: provided, further, said holders of title or evidence of title shall hold such title or evidence of title to at least one-fourth (1/4) part of the total area of the land in the proposed district, exclusive of state and government land which will be assessable for the purposes of the district. The equalized county assessment roll next preceding the presentation of a petition for the organization of an irrigation district shall be sufficient evidence of title for the purpose of this title, but other evidence may be received, including receipts or other evidence of the rights of entrymen on lands under any law of the United States or of this state, and such entrymen shall be competent signers of such petition, and the lands on which they have made such entries shall, for the purposes of said petition, be considered as owned by them.
Idaho Code § 43-101