In a groundbreaking ruling, the UK Supreme Court has said diplomatic cables leaked to WikiLeaks by whistleblower Chelsea Manning are admissible.

“The Supreme Court unanimously holds that the [WikiLeaks] cable should have been admitted into evidence," the bench ruled on Thursday, with five of the seven judges going against the lower court’s decision.

The ruling comes as a form of vindication for WikiLeaks founder Julian Assange, who tweeted that it was a “big win… that will affect many court proceedings around the world: leaked diplomatic cables are admissible as evidence.”

Big win at UK Supreme Court today in a judgment that will affect many court proceedings around the world: leaked diplomatic cables are admissible as evidence https://t.co/cFPoj86GsK — Julian Assange ⌛ (@JulianAssange) February 9, 2018

The case was brought by Chagos Refugees Group, representing Chagos Islanders who were expelled from their home in the Indian Ocean by the UK in the 1960s and ’70s. The islands were vacated to make way for a US Air Force base on Diego Garcia.

The displaced islanders have been fighting to return to their homelands for decades. The UK government wants to make the islands a marine park. This would ban fishing, which would affect the Chagossians’ ability to sustain a living should they be allowed to return home.

Thursday’s ruling focused on efforts to overturn a Court of Appeal decision that found there was no improper motive behind the marine park proposal.

Chagos islanders were evicted from their Indian Ocean homeland to make way for military colony https://t.co/HYIB6NMXhO — RT UK (@RTUKnews) November 16, 2016

The appeal centered on a US government cable published by WikiLeaks as part of the tranche of documents given to the organization by whistleblower Chelsea Manning. The Chagos islanders said the document showed the UK’s improper motive, but it had been excluded from proceedings earlier in the case.

The Supreme Court ruled that “the cable should have been admitted into evidence before the Administrative Court,” adding that “a majority of the Court dismisses the appeal on limb (i), that the exclusion of the cable by the Administrative Court could have had no material effect on the outcome regarding improper motive.”

Judgment has been given in R (on the application of Bancoult No 3) (Appellant) v Secretary of State for Foreign and Commonwealth Affairs (Respondent) https://t.co/OmzlqHHygjpic.twitter.com/F7PgbxgqI6 — UK Supreme Court (@UKSupremeCourt) February 8, 2018

"The Supreme Court unanimously holds that the [WikiLeaks] cable should have been admitted into evidence" Historic win in UK Supreme Court today for the admissibility of diplomatic cables published by @WikiLeaks.Judgment: https://t.co/VaznOhSklo)Court summary: pic.twitter.com/zg4GrcMIex — WikiLeaks (@wikileaks) February 8, 2018

The 2009 cable sent from the US embassy in London to Washington conveys the UK’s interest in establishing a marine reserve in the area, which, the cable reads, “would in no way impinge on USG [US government] use of the BIOT [British Indian Ocean Territory], including Diego Garcia, for military purposes.”

According to the cable, the senior Foreign and Commonwealth Office (FCO) official agreed the US and UK should negotiate “to assure that U.S. interests were safeguarded and the strategic value of BIOT was upheld.”

The UK official “said that the BIOT's former inhabitants would find it difficult, if not impossible, to pursue their claim for resettlement on the islands if the entire Chagos Archipelago were a marine reserve,” the cable reads.

It also refers to the government’s thinking on the reserve that “there would be no human footprints” or “Man Fridays” on the islands, and that the park would “in effect, put paid to resettlement claims of the archipelago's former residents.”

Meet the historian determined to expose the UK government’s secrets https://t.co/Mha25w9jTK — RT (@RT_com) January 25, 2018

During the Administrative Court proceedings, objections were made about using the cable because of the UK’s Official Secrets Act and the government’s policy of “neither confirm nor deny” when it comes to such documents. It was also argued that it breached diplomatic privilege, which the court agreed with.

While the Administrative Court agreed the cable should not be used, the Court of Appeal said since the cable had already been disclosed to the world, admitting it into evidence wouldn’t have violated the US mission to London’s diplomatic privilege.

Thursday’s Supreme Court ruling also echoed the court’s earlier findings that the cable’s exclusion “had no material effect on the proceedings” and would not have made a difference to the decision.

Think your friends would be interested? Share this story!