In the latest vindication of NSA whistleblower Edward Snowden, a U.K. court ruled on Friday that the British government violated human rights law by failing to safeguard some aspects of its intelligence-sharing operations until December 2014.

The Investigatory Powers Tribunal found that the Government Communications Headquarters (GCHQ) accessed information obtained by the National Security Agency (NSA) without sufficient oversight, violating Articles 8 and 10 of the European convention on human rights. According to Reuters, "The tribunal's concern, addressed in the new ruling, was that until details of how GCHQ and the NSA shared data were made public in the course of the court proceedings, the legal safeguards provided by British law were being side-stepped."

The Guardian adds, "The ruling appears to suggest that aspects of the operations were illegal for at least seven years—between 2007, when the Prism intercept [program] was introduced, and 2014."

Article 8 guarantees the right to privacy; Article 10 protects free expression.

"For far too long, intelligence agencies like GCHQ and NSA have acted like they are above the law," said Eric King, deputy director of Privacy International, one of the human rights groups that brought the case to the IPT. "Today’s decision confirms to the public what many have said all along—over the past decade, GCHQ and the NSA have been engaged in an illegal mass surveillance sharing program that has affected millions of people around the world."

The New York Times reports:

Although privacy campaigners claimed the decision as a victory, many experts said the British and American intelligence agencies would continue to share information obtained with electronic surveillance, even if they had to slightly alter their techniques to comply with human rights law.

Named in the decision (pdf) were the NSA's controversial PRISM program, which whistleblower Edward Snowden revealed in 2013 as the invasive spying operations being conducted on U.S. citizens.

Investigative journalist Glenn Greenwald, who reported on Snowden's document leak, tweeted on Friday:

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Why did Edward Snowden have to make us aware of all this? Would have been so much better if we remained ignorant http://t.co/CrKCvLHziV — Glenn Greenwald (@ggreenwald) February 6, 2015

"We must not allow agencies to continue justifying mass surveillance programmes using secret interpretations of secret laws," King continued. "The world owes Edward Snowden a great debt for blowing the whistle, and today’s decision is a vindication of his actions."

IPT's decision marks the first time that the highly-secretive court has ever ruled against any of the U.K.'s intelligence services in its entire 15-year existence.

During IPT hearings in 2014, Matthew Ryder, a lawyer for civil rights group Liberty, charged that intelligence agencies were building vast databases from unlawfully obtained emails and other communications.

However, the IPT ruled in December last year that British and American intelligence agencies had brought their oversight policies in line with European law, and could continue sharing information legally.

A GCHQ spokesperson did not address the IPT's new ruling in a statement on Friday, focusing only on the court's December decision which allowed the agency to continue its spying operations. "We are pleased that the court has once again ruled that the U.K.’s bulk interception regime is fully lawful," the spokesperson said. "By its nature, much of GCHQ’s work must remain secret. But we are working with the rest of government to improve public understanding about what we do."

The privacy and human rights groups who brought the case against GCHQ to the IPT last year have also appealed that ruling.

"After a decade and a half of siding with the Government, it is welcome that the IPT is beginning to hold our spies to account," said Cori Crider, director of legal charity Reprieve. "But stark problems with the UK's surveillance system remain: for years the government has written itself a blank cheque to eavesdrop on confidential communications between lawyers and clients – even in cases where the Government itself is in the dock. This is totally unfair and undermines the core premise of our legal system."

The European Court of Human Rights in Strasbourg, France will hear the appeal by the end of the year at the earliest. It will potentially allow citizens who believe they were targeted by surveillance programs before December 2014 to petition the court for the information that has been collected about them.