Idaho constitution
Article XV
Section 1

The use of all waters
now appropriated, or that may hereafter be appropriated for sale, rental or
distribution; also of all water originally appropriated for private use, but which after
such appropriation has heretofore been, or may hereafter be sold, rented, or
distributed, is hereby declared to be a public use, and subject to the regulations and
control of the state in the manner prescribed by law.