A civil servant at the Foreign Office has been cleared of breaching the Official Secrets Act.
Derek Pasquill said he had been "completely vindicated"
Derek Pasquill, 48, of west London, was accused of making damaging disclosures by leaking confidential documents to the New Statesman and the Observer.
The papers were said to refer to secret CIA flights and the UK's contact with Muslim groups.
His lawyer said a prosecution decision to drop charges was "vindication" that what he did was in the public interest.
Julian Knowles said the documents related to public debates on engaging with radical Islam and the practice of "extraordinary rendition" - the US transportation of terror suspects to secret prisons.
The judge was told internal Foreign Office documents disclosed as part of the legal process would have undermined the prosecution case.
Mr Pasquill said he had been through a "very unpleasant ordeal" but that he had been "completely vindicated in my actions in exposing dangerous government policy and changing its priorities".
He told BBC 2's Newsnight that he felt the information was of "such importance" that it was right to leak the documents to a journalist "in order for that information to be discussed and debated".
"I thought this information deserved to make an impact in public and I took the steps that I did on that basis," he said.
It was better to have these issues debated in public than leave them to "a small group of officials who are driving a policy", he added.
New Statesman editor John Kampfner described Mr Pasquill's prosecution as a "misguided and malicious move".
He said a number of government ministers had "privately acknowledged" that the information provided by Mr Pasquill had been "in the public interest and was responsible in large part for changing government policy for the good".
Mr Pasquill, who was arrested in 2006, remains suspended on full pay from his job as a desk worker.
The Foreign Office said that passing on official documents was "absolutely contrary" to good government.
It suggested that Mr Pasquill "may be subject to internal disciplinary procedures".