In August 2012, the Colorado Court of Appeals issued a decision which affects annulments in Colorado in two important ways:  (1) it approved marrying for a green card as a basis to find a fraudulent marriage, and (2) it held that a spouse who fraudulently induced the other to marry is not entitled to maintenance or a share of the marital estate beyond that spouse's own financial contributions.  In re: the Marriage of Joel, 2012 COA 128.

In 2012, the Colorado Assembly enacted S.B. 12-56, which provides that various parenting professionals must, within 7 days of appointment, provide the parties, counsel and court with a disclosure of the nature of any familial, social, or financial relationship with a party, counsel, or judge.  Each party then has 7 days to object, or the objection is waived.

Colorado Revised Statute 14-10-120.3 has long permitted a couple to obtain a decree of dissolution when they had complete written agreements, and either (1) both spouses had counsel, or (2) there were no minor children.  But, due to a quirk in the statute, it only applied to a decree of dissolution.

See this article on Putative Spouses in Colorado for an alternative when someone is unable to prove a valid marriage, but has a good faith belief he/she was married.  

See the newly-expanded section on Common Law Marriage in Colorado, with more discussion of the factors courts look at, and citation to specific judicial decisions.