The 49-year-old Australian is being charged in the US with espionage for his role in publishing classified military and diplomatic cables.
“I have decided that extradition would be oppressive and I order that he be dismissed,” Judge Vanessa Baraitser said in her ruling on Monday.
Despite the decision that Assange would receive a “fair trial” in the case of extradition to the United States, the judge was of the opinion that the “special administrative measures” that Assange would probably follow would have a serious negative effect on his mental health have.
“I find that the mental state of Mr Assange is of such a nature that it would be oppressive to extradite him to the United States of America,” she added.
The US has said it will appeal against the decision.
This is a breaking story, more to follow.