Breivik, made the defiant gesture as he entered the courtroom at the start of the hearing about his detention since he massacred 77 people in 2011.
Judge Oeystein Hermansen told him the salute was insulting and should not be repeated.
Breivik made a similar salute at the start of the lower court hearing last year where the judge agreed with him that his near-isolation in jail violated a European Convention on Human Rights ban on “inhuman and degrading treatment”.
Launching the state’s appeal, Attorney General Fredrik Sejersted defended the draconian measures, including hundreds of strip searches and no contact with other inmates, as fully justified for an unrepentant far-right extremist.
“There is no human rights violation,” Sejersted said.
“He has not broken down, he has not expressed remorse, he is proud of what he has done,” he told the court, saying Breivik seemed ever more convinced of his extreme right-wing ideology.
On July 22, 2011, Breivik killed eight people with a car bomb outside the prime minister’s office in Oslo and then gunned down 69 others on an island near the capital, many of them teenagers attending a youth camp of Norway’s then-ruling Labour Party.