Canada

No formal re-registration process

Canada doesn’t have a national process for “re-registering” a foreign marriage. As long as the marriage is legal according to the law of the place where it happened, and complies with Canada’s own federal marriage law (things like both parties being of legal age and not already married to someone else), it’s recognized without any extra Canadian paperwork. Your apostilled Colorado marriage certificate is the document you’d show for any Canadian administrative purpose. See the apostille process.

Canadian courts apply this through a clean two-part test: formal validity (whether the ceremony itself followed the right procedure) is judged under the law of the place where it happened; essential validity (capacity to marry, like age and prior marriages) is judged separately under the law of where each of you was domiciled beforehand. Since Colorado law affirmatively permits self-solemnization, that satisfies the formal validity half.

Canada's Criminal Code makes it an offence to solemnize a marriage without being authorized to do so, but that's a rule about performing ceremonies in Canada, not a test applied to a foreign marriage's recognition. We found no Canadian case addressing a self-solemnized marriage by name, so the two-part test above is a well-corroborated general framework, not a tested outcome for this exact scenario. Provincial family law can add nuance (Ontario, for instance, has a separate "good faith marriage" exception for cases with missing paperwork, which isn't the scenario you'd be in with a properly issued Colorado certificate). If something provincial-specific matters for your situation, confirm with a Canadian family law practitioner.

No Certificate of No Impediment beforehand

Colorado doesn’t ask foreign nationals for anything equivalent to a pre-marriage “no impediment” document; a valid passport is the ID requirement. See colorado counties compared for county-specific notes as we gather them.

The practical summary

• Your Colorado marriage is valid in Canada the moment it’s valid in Colorado; there’s no separate Canadian registration step.
• Keep your apostilled certificate as your proof of marriage for any Canadian administrative purpose.
• You won’t need a CNI-equivalent document to marry in Colorado in the first place.
• Given the shorter drive/flight from most of Canada, also see scenic spots within 2 hours of Denver and planning your trip if you’re weighing whether to drive down rather than fly.

See does it matter what country we’re from? for the broader picture of why this varies country to country.