The Guardian reports: In fiction, James Bond drew quite judiciously upon his licence to kill, bumping off just 38 adversaries in a dozen Ian Fleming novels. In each case, the individual received his or her just deserts.

In real life, MI6 insists its officers do not kill anyone. “Assassination,” its former head Sir Richard Dearlove has said, “is no part of the policy of Her Majesty’s government” and would be entirely contrary to the agency’s ethos.

But there can be circumstances in which MI6 officers do have a licence to kill or commit any other crime, enshrined in a curious and little-known law that was intended to protect British spies from being prosecuted or sued in the UK after committing crimes abroad.

Section 7 of the 1994 Intelligence Services Act offers protection not only to spies involved in bugging or bribery, but also to any who become embroiled in far more serious matters, such as murder, kidnap or torture – as long as their actions have been authorised in writing by a secretary of state.

And as such, the section is certain to come under intense scrutiny in the months ahead, as detectives and human rights lawyers pore over the details of the secret rendition operations that MI6 ran in co-operation with Muammar Gaddafi’s regime in 2004.

Last month Scotland Yard and the Crown Prosecution Service announced that the operations, in which two leading Libyan dissidents were abducted and taken to Tripoli with their families, were to be the subject of a criminal investigation.

A few days later lawyers for both families began civil proceedings against Sir Mark Allen, the former head of counter-terrorism at MI6, accusing him of complicity in their “extraordinary rendition”, torture and inhuman and degrading treatment. Proceedings against the government, MI6 and MI5 are to follow.

The case is based in large part upon a batch of documents discovered in an abandoned Libyan government office last September. These showed that the abductions were plotted with the help of MI6: it was all part of the rapprochement between Gaddafi and the UK and US that saw the dictator abandon his WMD programme and open oil and gas exploration opportunities to western firms.

When a researcher for Human Rights Watch stumbled upon the documents, no attempt was made to deny MI6 involvement in the rendition operations they described.

Instead, Whitehall sources immediately said the operations were part of “ministerially authorised government policy”. The statement was intended as a clear signal that a secretary of state had signed off a “clause 7 authorisation” under the Intelligence Services Act.

Section 7 is entitled Authorisation of Acts outside the British Islands, and says: “If, apart from this section, a person would be liable in the United Kingdom for any act done outside the British Islands, he shall not be so liable if the act is one which is authorised to be done by virtue of an authorisation given by the secretary of state under this section.”

It adds that liable in the United Kingdom “means liable under the criminal or civil law of any part of the United Kingdom”.

The “acts” can take place only overseas and remain illegal both under the laws of the country where they are committed and possibly under international law. But, section 7 says, with the stroke of a pen a secretary of state can rule that no UK law can be brought to bear.