“The recent ruling of the Court of Appeal that the Airports NPS [National Planning Statement] was unlawful for failing to take account of the Paris Agreement exposes the cracks in the government’s approach to strategic decision-making…”

So reads the crowd-funding page for the Good Law Project’s latest venture, which aims, in their own words, to “force” the Government to “reverse the structural bias in the planning system in favour of fossil fuels and against renewables”.

This sort of thing won’t do anything to dissuade those who think the Heathrow ruling represents another example of the judiciary overreaching themselves and getting involved in politics – which in turn makes it more important to understand what happened in that judgment.

Picking through rulings like this is a challenge for non-lawyers (one reason the judicialisation of politics, when it does occur, is so democratically problematic), and planning law can be fiendishly complex. But this post, by David Hart QC on the ‘UK Human Rights Blog’, is an excellent introduction to what happened in this case.

The prominent role of the Paris Agreement has led some to believe that the ruling represents an attempt to give effect to a treaty without it being directly implemented in domestic law via statute. This impression is likely bolstered by reading the original High Court judgment, which noted (para 606) that:

“It is well-established that English law is a dualist legal system under which international law or an international treaty has legal force at the domestic level only after it has been implemented by a national statute … Therefore, none of them having been incorporated, any obligation imposed on the UK Government by the Paris Agreement has no effect in domestic law.”

The above is true, and directly imposing obligations on the Government from the Paris Agreement would be a severe breach of the proper role of the courts. But that’s not what happened. The real culprit, as far as a humble non-lawyer such as me can tell, is an entirely domestic bit of legislation: the Planning Act 2008.

In its ruling, the Court of Appeal found the Government in breach of its obligations under two parts of that Act, s.5(8) and s.10(3), which can be found here and here. Section 5(8) reads:

“The reasons must (in particular) include an explanation of how the policy set out in the statement takes account of Government policy relating to the mitigation of, and adaptation to, climate change.”

And Section 10(3) reads:

For the purposes of subsection (2) the Secretary of State must (in particular) have regard to the desirability of—

(a) mitigating, and adapting to, climate change;

(b) achieving good design.”

Basically the Government has a duty, under the Planning Act, to explain how it is accounting for its own climate change policy.

The difference between the two rulings arises over whether or not the Paris Agreement is government policy. The High Court decided it was not, presumably due to it not being put on a specific statutory footing (which would unquestionably bring it within the legal nexus that frames government policy), whilst the Court of Appeal decided it met the threshold, having been ratified as well as being endorsed in the Commons, to qualify under the terms of an existing statute, the Planning Act.

(It’s important to note that it does not appear that even the Court of Appeal’s interpretation would actually oblige the Government to adopt or eschew any given policy when it comes to Heathrow, merely to ensure that they had dotted every i and crossed every t whilst reaching the decision.)

Of course, it might suit the Prime Minister to allow a judicial bogeyman to cover a very handy excuse to abandon a Heathrow scheme to which he was personally opposed. But even without misrepresenting it, this case illustrates that there is more than one way for high-minded politicians in previous parliaments to set snares for their successors.

What tripped the Government today was not the imposition of abstract yet legally-binding end goals (although that may come), but the enforcement of vague but legally-binding procedural rules. It’s easy for legislators to insist that the drafters of future legislation “must have regard for the desirability of” this or that, but much harder to predict how judges or indeed government lawyers will interpret those sentences.

Nor, even more importantly, can those same politicians gauge the extent to which the gradual accretion of such requirements will bog down decision-making over the long term..

As I have argued elsewhere, if the Government truly wants to avoid things like this it will need to “conduct a review into all the legal obligations currently laid upon it by preceding parliaments and make a deliberate push for a shift away from this style.” But are politicians really ready to clear-cut such a useful thicket of political cover?