Idaho Code § 31-1411
After the organization of a fire protection district, additional contiguous or noncontiguous territory lying within the same county may be added thereto and shall thereupon and thenceforth be included in such district. Territory that is not contained in an existing fire district, and is not immediately adjoining the boundaries of the fire district into which annexation is sought, may be annexed into the district provided the territory consists of not less than forty (40) contiguous acres. At least seventy-five percent (75%) or more of the owners or contract purchasers of the land sought to be annexed shall petition the fire protection board and request annexation of the territory particularly described in said petition. Upon receipt of any such petition the fire protection board shall hold a hearing not less than ten (10) nor more than thirty (30) days thereafter, or upon the written consent of the petitioner within one hundred eighty (180) days, and said board shall cause notice of such hearing, designating the time and place, to be published in at least one (1) issue of a newspaper of general circulation within the district. Any person supporting or objecting to such petition shall be heard at such hearing, if in attendance, and at the close of such hearing said board shall approve or reject said petition. If the board approves said petition it shall make an order to that effect and certify a copy of said order containing an accurate legal description of the annexed territory to the board of county commissioners of the county where said fire district is situated. Said board of county commissioners shall thereupon enter an order of annexation and cause the same to be recorded so as to include the annexed property on the tax rolls as in this chapter provided.
In the event that more than twenty-five percent (25%) of the owners or contract purchasers of the land sought to be annexed do not join in said petition, and the board determines by resolution entered on the minutes of the board, that the annexation would be in the best interests of the district and that an election on the issue should be held, additional territory may nevertheless be annexed by the affirmative vote of a majority of the qualified electors of such additional territory voting on the question at an election held therefor, which vote may be taken at an election held as provided in section 31-1405, Idaho Code. The same procedure shall be adopted as provided in sections 31-1402 through 31-1406, Idaho Code.
If owners or contract purchasers of territory located within an existing fire protection district seek to petition to be annexed into another fire protection district, they must demonstrate that they are likely to receive an improved response to requests for services from the other fire protection district and obtain written approval of the board of the fire protection district within which the territory is already located. The written approval must be attached to their petition to annex. The procedure for the annexation petition shall be the same as otherwise provided in this section.
Idaho Code § 31-1411