Could you please report where you read this? According to the official website for Norwegian laws, Lovdata.no, there was no such exemption to paragraph 2 of the Norwegian constitution of May 17th 1814. The paragraph goes as followed(this is my own translation, sadly i dont think they have an english version of it)

The Evangelical-Lutheran religion will continue to be the official religion of the state. The population must follow it, and is obliged to raise their children to follow it. Jesuits and monastic orders must not be accepted. Jews are still forbidden from entering the realm.