In his first day of testimony on Thursday, Mullah Krekar compared his group's struggle to establish a strict Islamic society in Kurdish areas of northern Iraq with that of the Jewish people 60 years ago, when they sought to establish Israel as a nation.
Krekar has been a refugee in Norway since 1991 and has taken the government to court over an order to deport him as a threat to national security.
Erna Solberg, the minister of local government whose portfolio includes refugees, has said there is information indicating that Krekar remains a threat to Norwegian security.
Even though Norwegian police dropped all charges against Krekar in June 2004, citing lack of evidence and fears that witness testimony in Iraq was coerced, Solberg upheld a 2003 order to strip him of his refugee status and deport him.
Solberg said national security issues do no require the same level of proof as criminal cases.
Krekar's case, which began in the Oslo city court, is expected to take about two weeks.
However, appeals are expected to take years.
Born Najm al-Din Faraj Ahmad, Krekar founded the Islamic fundamentalist group listed as a "terrorist" organisation by the United States and the United Nations.
Ansar al-Islam is also suspected in bombings against US-led forces in Iraq.
Krekar has said he no longer leads the group and has repeatedly denied terrorism allegations or links to al-Qaida.
He was arrested at an airport outside Amsterdam in September 2002, after Iran denied him entry and sent him back to Europe.
He was deported to Norway in January 2003, and interrogated by intelligence services in both countries.