A coalition of local councils, environmental activists and London residents claims the government has failed to properly address the impact on air quality, climate change, noise and congestion that adding a third runway would entail. London Mayor Sadiq Khan had also backed the lawsuit.
But the court ruling, which can be appealed, supports the plan to make Europe's biggest airport even bigger. Britain's Parliament last year approved the project, which the government describes as the most important transportation decision in a generation.
The 14 billion-pound (currently $18.3 billion) project followed decades of study and argument over how to expand airport capacity in southeastern England. Prime Minister Theresa May has said the expansion will boost economic growth.
Heathrow rejoiced in the decision, pledging to get on with the project "that will connect Britain to global growth, providing thousands of new jobs and an economic boost for this country and its future generations." Transport Secretary Chris Grayling urged "all public bodies not to waste any more taxpayers' money or seek to further delay this vital project."
But those most directly affected pledged to fight on. "This is not the end of the matter," said Gareth Roberts, who leads the local council for the neighborhood of Richmond, over which planes fly low as they approach the airport. "We defeated a previous government on Heathrow back in 2010. We won then for our residents and we can win again in the future. A runway that breaches legal air quality limits simply cannot be built and opened."
The environmental group Greenpeace said that while the campaigners may have lost this judgment, the government is losing the argument on whether such expansion is "morally justifiable." The government's decision in favor of the north-west runway proposal was challenged by several local councils affected by the decision as well as the mayor of London and environmental groups such as Greenpeace, Friends Of The Earth and Plan B.
The councils and other opponents argue that the additional runway would effectively create a "new airport," with severe consequences for the capital. They claimed the government statement setting out its support for the project failed to properly address the project's impact.
The High Court dismissed the arguments, though it acknowledged views of the opponents were strongly held. "There was a tendency for the substance of the parties' positions to take more of a center stage than perhaps it should have done, in a hearing that was only concerned with the legality, and not the merits, of the Airports National Policy Statement," Judge Gary Hickinbottom said in the ruling.