Telluride decision: The city of Telluride was sued by developers and this case law is found in Town of Telluride v. THIRTY-FOUR VENTURE in 2000. The Supreme Court of Colorado ruled that requiring developers to set aside a portion of units that would be rented at below-market-rate in new projects is illegal. It is considered a form of rent control that was banned by the state legislature in 1981. You can view that language HERE.
HB21-1117: Local Government Authority Promote Affordable Housing Units. The Act clarifies the authority of cities and counties to plan and regulate the use of land in order to promote the construction of affordable housing units; it creates one or more alternatives to the construction of affordable housing. It is stated in Section 2, subsection (e.5) (1) that this is NOT a form of rent control. https://leg.colorado.gov/sites/default/files/2021a_1117_signed.pdf