By Mick Krever, CNN

CIA agents who tortured inmates can be prosecuted anywhere in the world, the United Nations Special Rapporteur for Human Rights and Counter-Terrorism, Ben Emmerson, told CNN’s Christiane Amanpour on Thursday.

“They are considered as war crimes, they are crimes of international jurisdiction,” he said.

“Any country in the world can prosecute CIA agents involved in this activity, and Italy already has prosecuted, convicted 22 CIA agents, including the Milan station chief, and sentenced them to significant periods in prison in absentia.”

Italy sentenced the agents, including CIA station chief Robert Seldon Lady, to prison in absentia in 2009 for their role in the alleged CIA capture of a Muslim cleric on the streets of Milan; prosecutors there said that Osama Mustafa Hassan Nasr was then rendered to Cairo, where he was tortured.

This danger of prosecution, of course, means that any CIA agent involved in the program could potentially be arrested whenever he or she leaves the United States.

A former chief prosecutor at Guantanamo Bay, Colonel Morris Davis, told Amanpour on Tuesday that “my advice would be vacation domestically.”

When the U.S. Senate released its report on torture by the CIA during the Bush Administration, Emmerson released a statement calling the program a “criminal conspiracy.”

“It's not a matter of opinion,” Emmerson told Amanpour. “It's a matter of legal interpretation.”

“Torture is a crime. The acts that were committed are undoubtedly torture and cross the line into that territory by a very considerable distance; there was an agreement among senior officials to implement that program; and there was a spurious legal cover given by the Office of Legal Counsel.”

“All of those involved are guilty of an agreement between them to commit what amounts to a crime, or a series of crimes. And those crimes must as a matter of international law be prosecuted.”

There are three ways, he explained, that those prosecutions could come.

First responsibility, he said, lies with the U.S. itself, and the attorney general.

Prosecutions by the U.S. itself, however, seem very unlikely. In 2012, the Department of Justice said that “the Department would not prosecute anyone who acted in good faith and within the scope of the legal guidance given by the Office of Legal Counsel regarding the interrogation of detainees.”

That, however, is an “untenable position,” Emmerson said.

“As far as the U.S. obligations under the torture convention are concerned, there must be prosecutions whether or not this was authorized, and indeed, those involved in the authorization itself are criminally responsible.”

The second way prosecutions could arise is that other countries could bring charges, as Italy did in 2009.

“And the third possibility is that the office of the prosecutor of the International Criminal Court is currently investigating the abuse by U.S. forces and the CIA of detainees in the notorious Salt Pit black site in Afghanistan.”

The fact that the U.S. is not signatory to the ICC, he said, makes no difference for those purposes, because Afghanistan is.”

The first priority, he said, must be for America itself to “reopen that process of inquiry in order to consider not just those who acted on the ground, incompatibly with their orders, but those higher up who conceived of this operation and who gave it spurious and entirely tendentious legal justification.”