The UK's Government Communications Headquarters (GCHQ) acted unlawfully in accessing millions of people’s private communications collected in bulk by the US National Security Agency (NSA), the Investigatory Powers Tribunal has ruled.

The tribunal found that the intelligence-sharing relationship was unlawful prior to December 2014, because rules governing the UK’s access to the NSA’s mass electronic surveillance programs PRISM and Upstream were secret.

Landmark ruling

The landmark ruling is the first time the tribunal, which considers complaints brought against GCHQ, MI5 and MI6, has found against the intelligence agencies in its 15-year history.

The data-sharing agreement between the US and UK came to light last year during legal proceedings – brought by Liberty, Privacy International and Amnesty International – challenging GCHQ’s surveillance practices in the wake of the Snowden revelations.

Limited safeguards

In December 2014, the tribunal held that GCHQ’s access to NSA intelligence was lawful from that time onward because secret policies governing the UK-US relationship were made public during the case.

Liberty disagrees that the limited safeguards revealed are sufficient to make GCHQ’s mass surveillance and intelligence-sharing activities lawful, and will challenge the tribunal’s December decision at the European Court of Human Rights.

James Welch, legal director for Liberty, said: "We now know that, by keeping the public in the dark about their secret dealings with the National Security Agency, GCHQ acted unlawfully and violated our rights. That their activities are now deemed lawful is thanks only to the degree of disclosure Liberty and the other claimants were able to force from our secrecy-obsessed government.

“But the intelligence services retain a largely unfettered power to rifle through millions of people’s private communications – and the tribunal believes the limited safeguards revealed during last year’s legal proceedings are an adequate protection of our privacy. We disagree, and will be taking our fight to the European Court of Human Rights."