The power of the Paris climate agreement – court stops the expansion of London airport

In its ruling of 27 February 2020, the British Court of Appeal stopped the expansion of London's Heathrow Airport for the time being. The judges found that the plans to set up a new runway had been drawn up without taking into account the Paris Climate Agreement and national climate protection targets and were therefore unlawful.


London Heathrow Airport is the largest airport in Europe and the sixth largest in the world, with 80 million passengers a year. A third runway was now to be added to the two existing ones. Environmental organisations, residents' groups and even the Mayor of London had filed complaints against these plans. A total of three different lawsuits had been filed, alleging violations of nature conservation and climate protection laws. While the suits had been dismissed by the Divisional Court, the Court of Appeal has now ruled in favour of the plaintiffs.

The decision

The Court of Appeal had to deal with various legal questions concerning the planned major project. The decisive factor in the judges' decision was ultimately the failure to comply with the Paris Climate Convention.

In 2016, the United Kingdom ratified the Paris Climate Convention, thereby committing itself internationally to helping to limit the rise in temperature to below 2°C compared to pre-industrial levels. The country had also committed itself to the goal of achieving greenhouse gas neutrality by 2050.

Nevertheless, these requirements of the Paris Climate Agreement were not taken into account when planning the expansion of London Heathrow Airport. Instead, those responsible felt that they were not legally obliged to take climate protection targets into account.

The Court of Appeal countered this view with its ruling. By ratifying the international treaty, the government had committed itself to the agreement. For this reason, the climate protection objectives had to be taken into account in government decisions. However, the Paris Climate Agreement had not been taken into account in the planning of the airport expansion. Thus, the decision to build a third runway was legally flawed. Since the fight against climate change is a matter of the highest national and international importance, a violation must also result in the decision of the project having no further legal effect. The judges therefore declared the decision to be unlawful.


It was important to the judges of the Court of Appeal that their judgment not be misunderstood. The judgment therefore concludes with a summary of the reasons, with which the judges once again emphasised what their decision means - and what it does not.

In particular, the decision does not rule out the possibility of another runway at Heathrow Airport for all time. Although the judges declared the government's decision to build the runway unlawful, they did not declare the airport extension in itself illegal. The court could not decide whether a third runway would be compatible with the UK's climate protection goals, this assessment was up to the government.

The government could therefore decide to expand the airport again, taking into account the binding climate protection goals. The third runway is thus not yet finally ruled out. However, a continuation of this project under the government of Boris Johnson seems rather unlikely. The Prime Minister is one of the declared opponents of the expansion of the airport and had already announced that he would lay down in front of the construction machines if necessary to stop the project.

Nevertheless, the ruling represents a groundbreaking decision. This is because the Court of Appeal has for the first time made it clear that the objectives of the Paris Climate Agreement are binding on the British government and must be taken into account when making decisions.

It is now no longer possible to simply ignore the national and international climate protection goals, as happened when planning the airport expansion. If, however, a decision is taken without taking the climate protection targets into account, the decision will be illegal. The ruling thus clearly shows the power inherent in the Paris climate agreement. The German legal system is also not unfamiliar with the need to take into account climate-protection objectives in emission-intensive planning projects. Already in 2009, the development plan for the hard coal-fired power plant Datteln IV had been declared null and void by the Higher Administrative Court of North Rhine-Westphalia (OVG NRW) on the grounds, among others, that the state planning objectives for climate protection had not been observed sufficiently in its preparation (OVG NRW, judgement of 3 September 2009 - 10 D 121/07).

Dr Gernot-Rüdiger Engel

Dr Gernot-Rüdiger Engel
+49 40 18067 16639