In a verdict that will have shocked ministers and energy companies the jury at Maidstone Crown Court cleared six Greenpeace activists of criminal damage, reported the Independent.
Jurors accepted defence arguments that the six had a "lawful excuse" to damage property at Kingsnorth power station in Kent to prevent even greater damage caused by climate change.
The defence of "lawful excuse" under the Criminal Damage Act 1971 allows damage to be caused to property to prevent even greater damage - such as breaking down the door of a burning house to tackle a fire.
The not-guilty verdict, delivered after two days and greeted with cheers in the courtroom, raises the stakes for the most pressing issue on Britain's green agenda and could encourage further direct action.
Kingsnorth was the centre for mass protests by climate camp activists last month. Last year, three protesters managed to paint British Prime Minister Gordon Brown's name on the plant's chimney. Their handiwork cost Â£35,000 to remove.
The plan to build a successor to the power station is likely to be the first of a new generation of coal fired plants.
As coal produces more of the carbon emissions causing climate change than any other fuel, campaigners claim that a new station would be a disastrous setback in the battle against global warming, and send out a negative signal to the rest of the world about how serious Britain really is about tackling the climate threat.
But the proposals, from the energy giant E.ON, are firmly backed by the Business Secretary, John Hutton, and the Energy minister, Malcolm Wicks.
Some members of the Cabinet are thought to be unhappy about them, including the Foreign Secretary, David Miliband, and the Environment Secretary, Hilary Benn. Mr Brown is likely to have the final say on the matter later this year.