He's apparently claimed necessity under section 47 of the Norwegian penal code and did the white power salute while being sworn in.
Section 47 of the Norwegian penal code...
"No person may be punished for any act that he has committed in order to save someone's person or property from an otherwise unavoidable danger when the circumstances justified him in regarding this danger as particularly significant in relation to the damage that might be caused by his act."
He's clearly loving all the attention he's getting, his defence team are even calling the cleric who founded radical Islamic group Ansar al-Islam, Mullah Krekar, as a witness to demonstrate how a person with extreme political views may be put on trial as sane so they don't think he's a nut job and dismiss his actions. He wants to be the next führer innit.