OSLO — He lives in a three-room suite with windows, about 340 square feet, that includes a treadmill, a fridge, a DVD player, a Sony PlayStation and a desk with a typewriter. He has been taking distance-learning courses at his country’s main university. He has access to television, radio and newspapers. He prepares his own food, and he entered the Christmas gingerbread-house baking contest at his prison.

Anders Behring Breivik, the Norwegian extremist who was convicted of killing 77 people in a bomb and gun rampage in 2011, returned to court on Tuesday to pursue his claim that his solitary confinement — albeit in cushy circumstances — violates his human rights.

The hearing, at which Mr. Breivik gave a Nazi-style salute, has been accompanied by a new round of grief and outrage over the attacks, the deadliest violence in Norway since World War II.

Mr. Breivik, 37, was convicted of terrorism in 2012 and sentenced to 21 years in prison, though he can be held for longer if he is deemed a threat to society.