By Gillian Hargreaves
BBC News political correspondent
The decision not to prosecute senior Tory MP Damian Green and junior Home Office worker Christopher Galley raises some pertinent questions for the government - and Her Majesty's Opposition.
Mr Green maintained throughout the affair that he had done nothing wrong
Did political anger over the damage caused to Labour's reputation by repeated leaks influence the Metropolitan Police's decision to hold an investigation in the first place?
Crucially, did frustration at the Home Office lead officials to give an exaggerated impression of the damage done?
For more than two years there had been mounting anger that restricted or unauthorised material had been leaked to the Conservatives.
Sources close to Home Secretary Jacqui Smith have made it very clear to me that there was huge frustration.
They are far from satisfied over the decision not to charge Mr Green or Mr Galley.
The sources point out that the director of public prosecutions said it had been right to call the police to investigate as soon as a pattern of leaks was established.
They also highlight that the Crown Prosecution Service (CPS) said the relationship between Mr Green and Mr Galley had breached the standards expected of those in public service.
Now the home secretary has ordered a review of the whole case.
And Mr Galley, who has been on leave for the past six months, will face disciplinary action.
This saga also raises questions about the role of the opposition and what its MPs get up to in Parliament.
Should they try to find examples of government wrongdoing and expose them? Even if it means relying on leaks from civil servants who may be breaking their own terms of employment and have their own political agenda?
In 1989 the government loosened the remit of the Official Secrets Act to prevent a repeat of the high-profile trials of Whitehall officials which dominated the 1980s.
The Commons home affairs select committee - which published its own report into the Green affair shortly before the CPS said there would be no charges - came to the conclusion that much of what had been leaked could never come under the banner of serious state secrets.
And there was little risk to the security of the country.
But the CPS's comments also pose a challenge for ambitious MPs who want to unearth a government's dirty laundry.
It made it very clear that they could still be prosecuted if information is leaked which would breach national security.
Each complaint to the police would be examined on a case-by-case basis and, depending on the seriousness of the leak, MPs could still find themselves explaining their actions before judge and jury - unlike Mr Green.