C.R.S. § 42-3-119

(1) The department shall not grant an application for the registration of a vehicle in any of the following events: (a) When the applicant for registration is not entitled thereto under this article; (b) When the applicant has neglected or refused to furnish the department with the information required on the appropriate official form or reasonable additional information required by the department; (c) When the registration fees required by law have not been paid; (d) When a certification of emissions control is required pursuant to part 4 of article 4 of this title, and such certification has not been obtained.