Colo. Const. art. XIV, § 3
Except as otherwise provided by statute, no part of the territory of any county shall be stricken off and added to an adjoining county, without first submitting the question to the registered electors of the county from which the territory is proposed to be stricken off; nor unless a majority of all the registered electors of said county voting on the question shall vote therefor.
Source: Entire article added, effective August 1, 1876, see L. 1877, p. 66. Initiated 74: Entire section was amended, effective upon proclamation of the Governor, December 20, 1974, but does not appear in the session laws. L. 84: Entire section amended, p. 1144, effective upon proclamation of the Governor, L. 85, p. 1791, January 14, 1985.
Cross references: For annexation of part of a county to an adjoining county, see §§ 30-6-105 to 30-6-109. 7.