1. If you have been granted Norwegian citizenship, but does not get a release from your previous citizenship.
2. If the decision is invalid.

More information on revocation is to be found in the Act on Norwegian Nationality § 26

1) Release of citizenship

It is generally a condition for Norwegian citizenship that the applicant within a year from the date of the decision provides a certificate of release from pervious citizenship. This condition does not apply if the citizenship is automatically released.

2) Invalid decision

If the applicant has given misleading or incomplete information, and this information had a considerable significance for the decision, the citizenship may be revoked.

The citizenship may also be revoked if the applicant has given information that was correct against his or her better judgement, would be of important relevance to the decision.