Right-wing extremist Anders Behring Breivik on Monday admitted massacring 77 people in Norway but pleaded not guilty, saying he was acting in self-defence.
Mr Breivik rejected the authority of the court on the first day of his long-awaited trial for the July 22 terrorist atrocities.
Eight people were killed in his bombing of Oslo's government district and 69 others died in his shooting spree at the Labour Party's youth camp on Utoya island.
"I don't recognise Norwegian courts because you get your mandate from the Norwegian political parties who support multiculturalism," Mr Breivik said in his first comments to the court.
"I admit to the acts, but not criminal guilt," he said, insisting he had acted in self-defence.
Mr Breivik has said the attacks were necessary to protect Norway from being taken over by Muslims.
He claims he targeted the government headquarters in Oslo and the youth camp to strike against the "cultural Marxists" he blames for allowing immigration in Norway.
Legal expert Jarl Borgvin Doerre said that while Norway has a principle of preventive self-defence in its law, that doesn't apply to this case.
"It is obvious that it has nothing to do with preventive self-defence," Mr Doerre said.
The key issue to be resolved during the 10-week trial is the state of Mr Breivik's mental health, which will decide whether he is sent to prison or into psychiatric care.
If deemed mentally competent, he would face a maximum prison sentence of 21 years or an alternate custody arrangement under which the sentence is prolonged for as long as he was considered a danger to society.
Survivors of the Utoya massacre, some of whom are attending the trial, are worried that Mr Breivik will use the trial as a platform for his neofascist views.
Mr Breivik wrote in a manifesto he published online before the attacks that "patriotic resistance fighters" should use trials "as a platform to further our cause."
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