The 15-page document discusses legality of restrictions on freedom of expression. [GALLO/GETTY]

The United Nations Human Rights Committee has issued a new authoritative commentary, setting tough rules limiting the extent to which states can restrict freedom of opinion and expression.

The committee released a document by a panel of 18 jurists on Thursday, who said freedom of opinion and by extension religion, should not be restricted under any circumstances.

The jurists set out their stance in a "general comment" on how parts of International Covenant on Civil and Political Rights (ICCPR) - a basic UN accord that outlines individuals' civil and political rights, and functions as one of the fundamentals in international human rights law - should be interpreted and applied.

Michael O'Flaherty, the committee's vice chairman, said on Thursday at a press conference in Geneva, that the 15-page document strongly reaffirms "the central importance for all human rights of the freedom of expression and sets out the very strict parameters within which the right can be restricted by states."

The comment interprets two paragraphs of the 1976 ICCPR, hitting at anti-terror laws, monopoly media, anti-blasphemy statutes and prosecution of maverick historians.

It also extends protection for freedom of expression to new media actors, including bloggers.

"Memory laws, which penalise the expression of opinions about historical facts, are unacceptable under the ICCPR, the comment states.

It also states that blasphemy laws are incompatible with the multinational treaty, except under very specific circumstances subject to strict requirements set out in the ICCPR.

"Freedom of expression is a necessary condition for the realisation of the principles of transparency and accountability that are, in turn, essential for the promotion and protection of human rights," the General Comment states.

"States parties should put in place effective measures to protect against attacks aimed at silencing those exercising their right to freedom of expression."

Application debate

At Thursday's media conference, the jurists commented on the recent debate over whether public or media criticism of Muslim practices - referred by some as "Islamophobia" - should be restricted.

The topic has been raging since last Friday's killings in Norway by an anti-immigration extremist, who killed close to 100 people in a near-simultaneous bombing in central Oslo and a shoot-out at a youth camp.

The committee's experts said that "prohibitions on displays of lack of respect for a religion or other belief system, including blasphemy laws", would violate "free speech" according to provisions of the ICCPR.

That interpretation would also make illegal efforts "to prevent or punish criticism of religious leaders or commentary on religious doctrine and tenets of faith". Islamic countries have long made such efforts.