Alleged computer hacker Lauri Love has won his appeal against extradition, but now faces prosecution in the UK.
A ruling by two High Court judges in London on Monday means that he will not be sent to the US.
But Lord Chief Justice Lord Burnett and Mr Justice Ouseley announced when allowing Love's extradition challenge: "We emphasise however that it would not be oppressive to prosecute Mr Love in England for the offences alleged against him. Far from it."
They said: "The CPS must now bend its endeavours to his prosecution, with the assistance to be expected from the authorities in the United States, recognising the gravity of the allegations in this case, and the harm done to the victims."
The judges said that, if proven, "these are serious offences indeed".
Mr Love, 32, who lives with his parents near Newmarket in Suffolk, was present in court to hear the ruling in his favour - which was greeted by a loud cheer from the packed public gallery.
The judges heard argument on his behalf during a hearing in November that extradition would not be in the "interests of justice" for a number of reasons, including the "high risk" that Mr Love, who suffers from Asperger syndrome, would kill himself.
After the ruling, Mr Love, speaking to reporters outside court, said: "This decision is important for the appropriate administration of criminal justice and also for the humanitarian accommodation of people whose brains work differently."
Authorities in America have been fighting for Mr Love to face trial on charges of cyber-hacking, which lawyers have said could mean a sentence of up to 99 years in prison if he is found guilty.
Mr Love, who also suffers from a depressive illness and severe eczema, is alleged to have stolen huge amounts of data from US agencies, including the Federal Reserve, the US army, the defence department, Nasa and the FBI in a spate of online attacks in 2012 and 2013.
His father, the Reverend Alexander Love, had said his son "fears for his life" because he did not think he could cope with the trauma of being sent to the US.