Contempt of court proceedings are being brought against an environmental lawyer who leaked the Supreme Court's decision about Heathrow's third runway.
Tim Crosland issued a statement to the Press Association revealing details of the court's judgement a day before it was due to be delivered.
It had been issued in confidence and was placed under embargo.
Mr Crosland said he leaked the draft judgement in an "act of civil disobedience".
On Friday the solicitor general, Michael Ellis QC MP, announced he will initiate contempt of court proceedings against Mr Crosland following a referral from the Supreme Court.
He said: "After careful consideration, I have concluded that in order that the rule of law be upheld, contempt of court proceedings should be brought against Tim Crosland.
"Irrespective of any personal views on any issue there is no excuse for knowingly undermining court processes and proceedings. As proceedings are now underway, it would not be appropriate to comment further."
The case has been referred to the Supreme Court.
Mr Crosland, a barrister and director of Plan B Earth, had been representing the eco-charity in an appeal brought by Heathrow Airport Limited.
Last month Mr Crosland said he broke the embargo to raise public awareness about the case.
"You have a short window for journalists to think about the outcome of a court case," he told the Law Society Gazette.
"It's only newsworthy for that 24 hours…My assessment was that if I waited for the judgment to be out and then say 'this is really dishonest' no one would have paid any attention. It wouldn’t have been noticed”.
