Idaho Const. art. III, § 8

(1) The regular sessions of the legislature must be held annually at the capital of the state, commencing on the second Monday of January of each year, unless a different day shall have been appointed by law, and at other times in extraordinary sessions when convened by the governor and in organizational sessions commencing on the first Thursday of December after the general election, unless a different day shall have been appointed by law.

(2) The legislature, while remaining a part-time, citizen legislature, must also be convened in special session by the president pro tempore of the senate and the speaker of the house of representatives upon receipt of a joint written petition of at least sixty percent of the membership of each house, specifying the subjects to be considered. Such special session must commence no later than fifteen days after the petition is received by the president pro tempore of the senate and the speaker of the house of representatives. At a special session convened pursuant to this section, the legislature shall have no power to consider or pass any bills or resolutions on any subjects other than those specified in the petition and those necessary to provide for the expenses of the session.