The Planning Act 2008 deals with authorisation of projects for the development of nationally significant infrastructure. Section 5 deals with National Polict Statements.
The Paris Agreement isa legally binding international treaty on climate change. It was adopted by 196 Parties in Paris on 12 December 2015 and entered into force on 4 November 2016. Its goal is to limit global warming to well below 2, preferably to 1.5 degrees Celsius, compared to pre-industrial levels.
The Secretary of State did not appeal the Court of Appeal's decision but Heathrow Airport Ltd (the owner of Heathrow) was permitted to appeal to the Supreme Court of the UK. The airport wishes to apply for development consent to carry the project through.
The Supreme Court (Lord Reed, Lord Hodge, Lady Black, Lord Sales, Lord Leggatt) has, unanimously, allowed the appeal -see Case summary etc.
Whether a Third Runway is ever constructed still depends on the proposal receiving development consent and environmental questions will be considered as part of that process.
Whether a third runway is required in practice is another matter. Civil aviation has seen an immense setback due to the impact of coronavirus on travel. There will be some recovery from this but civil aviation growth is difficult to forecast with confidence. This BBC report of 29 September offers an indication of the present day dire situation facing the aviation sector. The impact of Brexit on civil aviation also remains to be seen.
Following the Supreme Court's judgment, Heathrow Ltd commented - "This is the right result for the country, which will allow Global Britain to become a reality. Only by expanding the UK’s hub airport can we connect all of Britain to all of the growing markets of the world, helping to create hundreds of thousands of jobs in every nation and region of our country. Demand for aviation will recover from Covid, and the additional capacity at an expanded Heathrow will allow Britain as a sovereign nation to compete for trade and win against our rivals in France and Germany. Heathrow has already committed to net zero and this ruling recognises the robust planning process that will require us to prove expansion is compliant with the UK’s climate change obligations, including the Paris Climate Agreement, before construction can begin. The Government has made decarbonising aviation a central part of its green growth agenda, through wider use of Sustainable Aviation Fuel as well as new technology. As passenger numbers recover, our immediate focus will be to continue to ensure their safety and to maintain our service levels while we consult with investors, government, airline customers and regulators on our next steps."
In related news, the Supreme Court has referred a lawyer to the Attorney General. The Guardian 16 December reports - "The UK’s supreme court will refer a lawyer who broke the embargo on its ruling on Heathrow airport to the attorney general and the Bar Standards Board for investigation. Tim Crosland, the director of environmental charity Plan B Earth,
received the ruling in advance as one of the parties involved in the
case, and published his reaction on Tuesday, the day before the judgment
Media Centre Heathrow 11 November - Government leaves the UK's world class aviation sector out in the cold
Media Centre Heathrow 16 December - Heathrow's response to the findings of judicial review
The Guardian 16 December 2020 - Top UK court overturns block on Heathrow's third runway