The $18-billion project to expand London’s Heathrow Airport with a third runway was grounded by a senior court on Feb. 28 for not complying with the U.K.’s international climate change commitments. Heathrow Airport Ltd., the owner, says it will file an appeal with the U.K.’s Supreme Court.

The Appeal Court ruled that the government had “absolutely no legal means” to ignore its international climate change commitments under the Paris Agreement, according to Rowan Smith, an environmental law specialist at the law firm Leigh Day. The Dept. for Transport must now amend its Airports National Policy Statement (ANPS), which empowered the project in 2018.

Appeal Court judges reversed last May’s rejection by a lower court of a challenge to the project by a group of opponents, including the Mayor of London, local authorities and environmental groups.

Heathrow Airport Ltd. will “work with the government to fix the issue that the court has raised,” a spokesman said. Making the project compatible with climate commitments “is eminently achievable.” 

However, Secretary of State for Transport Grant Schapps stresses that the project is a private venture and securing its approval must be “industry led.” In a tweet he added: “airport expansion is core to boosting global connectivity. We also take seriously our commitment to the environment.”