Great Britain is learning the hard way why its leaders were foolish to join the 2015 Paris climate agreement and why American President Donald Trump pulled America out of the agreement. A British court has sided with environmental activists who sued to block construction of a runway at London’s Heathrow Airport, arguing that building the runway is not consistent with the government’s commitment to the Paris agreement.

Climate activists argue that traveling by airplane is one of the worst activities contributing to global warming, as carbon dioxide emissions per airplane passenger mile are much higher than that for mass transportation or even automobile travel. Accordingly, climate activists sued to block construction of the airport runway, using the British government’s signing of the Paris climate agreement as the legal hook to block construction.

By accepting the climate activists’ rationale and blocking airport runway construction, the British court delivered a wakeup call to America. When American climate skeptics have warned about such far-reaching enforcement of the Paris climate agreement, climate activists accuse skeptics of floating conspiracy theories. Yet, the British court decision shows how climate activists seek to use the Paris agreement to take away existing rights and how liberal judges are all too happy to oblige.

Ironically, the United Nations boasted that more than 20,000 climate activists and government officials flew to Madrid, Spain, last December for the 2019 United Nations Conference of the Parties climate talks.