On February 27, 2020, the Court of Appeal of England and Wales (Civil Division) issued its judgment in Plan B Earth v. Secretary of State for Transport [3]. The case involved a challenge to a 2018 decision (called an Airports National Policy Statement - ANPS) by the then Secretary of State, Chris Grayling, that identified Heathrow Airport as the preferred location for a new runway. The ANPS sets out a fundamental planning framework that, once finalized, cannot be challenged. Though several legal challenges against the ANPS were mounted, the successful challenge was based on the Secretary of State's failure to take into account the Paris Agreement [4] when taking his decision. The UK Climate Change Act 2008 [5] requires the Government to take into account climate change in its policy-making. This includes the Paris Agreement, which was ratified by the UK on November 17, 2016. When the Secretary of State was in the ANPS process, he received advice that he was not obliged to take the Paris Agreement into account. In response, the Court of Appeal stated: "In our view, that was a clear misdirection of law and there was, therefore, a material misdirection of law at an important stage in the process. That misdirection then fed through the rest of the decision-making process and was fatal to the decision to designate the ANPS itself."

Heathrow Airport argued that, had the Paris Agreement been taken into account at the time, the outcome would not have been substantially different and that the Agreement could have been taken into account later in the process. The Court was not persuaded and held that the Government was obliged to take it into account at every stage of the decision-making process, including the outset. The Court granted a declaration that the ANPS should not have legal effect until the Secretary of State reviews it in light of the UK's obligations under the Paris Agreement. It is not yet clear whether the decision will be appealed to the UK Supreme Court. For a more detailed summary of the judgment, see the blog [6] by David Hart QC.