Britain's High Court Friday rejected an appeal by a British man against his extradition to the United States to face charges of hacking into military computers. Gary McKinnon was arrested in 2002 and has been fighting to stay in Britain.

Briton Gary McKinnon lost his long legal battle Friday, and could face extradition to the United States as early as September.

McKinnon is charged with hacking into the computer networks of NASA, the Pentagon and other U.S. government agencies in 2001 and 2002 soon after the September 11, 2001, terrorist attacks.

McKinnon's lawyers had argued that their client, who suffers from Asperger's Syndrome, a form of autism, would be at risk of a mental breakdown or suicide if sent to the United States.

But the judges ruled that the extradition was lawful and proportionate to his crime, which U.S. prosecutors have called "the biggest military computer hack of all time."

Outside the court, McKinnon's mother, Janis Sharp, called the ruling a disgrace and made a plea to U.S. President Barack Obama for leniency.

"This is from the Bush era," she said. "It's not of Obama. He would not want this to happen. Robert Gates from the Pentagon said there's tens of thousands of extraditions every month. Are they going to extradite everyone? Or just one guy who has got Asperger's [syndrome] and was looking for UFOs, who had the naiveté to admit to computer misuse with no lawyer? And they thought, 'Soft touch, he'll do.' That's a reality."

In interviews with British media in 2006, McKinnon said he was looking for secret UFO technology.

"I was in search of suppressed technology, you know, laughingly referred to as UFO technology," he said. "I think it's the biggest kept secret in the world because of its value. Meanwhile, secretive parts of the secret government are sitting on suppressed technology for free energy."

McKinnon's lawyer said she would review the judgment and could appeal the High Court decision to Britain's Supreme Court or European courts on humanitarian grounds.