The 'FiveEyes' treaty
"...Since the signing in 1946 of the UKUSA Signals Intelligence Agreement, which first established the Five-Eyes partnership, it has been a convention that the allied intelligence agencies do not monitor one another's citizens without permission – an agreement often referred to publicly by officials across the Five-Eyes nations. However, a draft 2005 directive in the name of the NSA's director of signals intelligence reveals the NSA prepared policies enabling its staff to spy on Five-Eyes citizens, even where the partner country has refused permission to do so."
The newspaper notes, "terrorist's mobile phones, Taleban radio intercepts and e-mails by foreign intelligence agencies are all tracked from the distinctive doughnut-shaped building near Cheltenham that is home to Britain's principal electronic eaves-dropping agency. But now the 5,500 employees at the secretive GCHQ facility, and other listening posts in the UK, face claims that they might be 'parties to murder' by US drones under international law. Officials and analysts have told The Times that use of the electronic eavesdropping carried out by Britain's intelligence services is complicated by arrangements for information sharing that were established after the Second World War.
Under the terms of the secret 1946 UKUSA Agreement between Britain and the US, which is also known as the 'Five Eyes' system, Britain's network of listening stations is largely integrated and its intelligence pooled, with those of America and three other nations - Canada, New Zealand and Australia.
At the largest signal intelligence station in the world, Menwith Hill in Yorkshire, there is an RAF station commander, but three quarters of the near 2,000 staff are from America's National Security Agency. It acts as a ground station for US spy satellites as well as, allegedly, an interception station for traffic passing through commerical satellites.
Britain has other listening posts, including Ayios Nikolaous in Cyprus, an at GCHQ Bude, another joint US and UK operated station in Cornwall.
According to a 2001 European Parliament report, which investigated the extent of eavesdropping by the US and its partners, these constitute part of a global structure of interception stations. It encompasses US posts as far afield as Guam in the Pacific and Japan, Canadian stations in Labrador and Newfoundland as well as Australia and New Zealand-based listening posts along the Pacific Rim.
The Times undertands that signals intelligence generated by the system is pooled 'as far as possible', though British officials said they believed that the US held some of the most sensitive information back.
Officials and analytsts The Times spoke to said that such a web of exchange would lead to the possibility that British-generated intelligence could inform US drone strikes...."
Further links: British reliance on drones in Afghanistan prompts fears for civilians