The 33-year-old right-wing extremist has sent a letter to Norway's correctional services in which he criticizes the high-security regime he has been subjected to for more than a year, and the restrictions placed on his correspondence.
After his prison sentence was handed down on August 24th, Breivik has in practice been denied access to the computer which was provided for him, without internet, before the court ruling, lawyer Tord Jordet said.
Furthermore, all letters he sends and receives are censored as soon as politics is mentioned, he added.
"His freedom of speech is being violated," Jordet told AFP. "Being deprived of this freedom of expression breaches the constitution and human rights."
Breivik, who has been separated from other inmates since his arrest, has also complained over daily searches of his cell and of himself, and claims he is deprived of recreational and social activities.
"Such treatment isn't human," Jordet said.
The Norwegian Ministry of Justice declined to comment.
Breivik was given Norway's maximum sentence of 21 years in jail, which can be extended indefinitely. He is expected to spend most of that time at the Ila prison near Oslo.
In addition to his cell, he should also have access to an exercise room and a computer room.
However, access to those facilities is controlled by the prison authorities who, according to Jordet, haven't replied to his requests in recent weeks to use the computer.
Accusing his victims of fostering multiculturalism, Breivik on July 22nd last year detonated a bomb outside the centre-left government's headquarters and gunned down participants at a youth camp on the island of Utøya, killing a total of 77 people.