Reliance on the Paris Agreement in Climate Change Litigation: A Follow-Up


Hannah Taylor


Time to read

8 Minutes
Johan Hofvendahl, CC
Johan Hofvendahl, CC

In an article for the OUULJ Blog in March, I analysed the decision in Plan B and how it fit with trends in climate change litigation globally.[1][1] I concluded that the decision may give rise to a number of similar claims seeking to rely upon the Paris Agreement to challenge the Government over environmentally controversial decisions. Since then, the judgment in R. (on the application of Packham) v Secretary of State for Transport has been handed down.[2][2] This application for judicial review tried to use the reasoning on the legal implications of the Paris Agreement in Plan B to challenge the decision to continue with the High Speed 2 (HS2) project. The Court of Appeal distinguished Plan B, emphasising the limited scope of that decision and the reluctance of the judiciary to interfere with government decisions on issues which involve a careful balance of economic and social factors with the glaring climate emergency.


The case arose after the Secretary of State for Transport conducted the Oakervee review in 2019 into ‘whether and how to continue with the HS2 project’. The Divisional Court deemed this to be a costs/benefits review.[3][3] The review report indicated that the project should go ahead with measures to mitigate carbon emissions, amongst other things. On 11 February 2020 the Prime Minister announced the Government’s decision to continue with the project.

There were two grounds pleaded on appeal. Ground 2 was that the government erred in law by ‘misunderstanding or ignoring local environmental concerns and failing to examine the environmental effects of HS2 as it ought to have done’.[4][4] The Court of Appeal dismissed this conclusion for two main reasons. First, the cabinet ministers clearly did not intend to base their decision on whether to continue with the HS2 project solely on the Oakervee report, it was merely intended to inform the next steps.[5][5] Second, the report was not intended to undertake ‘a comprehensive assessment, or indeed any assessment, of the myriad of effects on the environment’.[6][6] Thus, it could not be concluded that the government made such an error as to believe that ‘the review report contained a full assessment of the project's environmental effects’.[7][7]

The important ground for the purposes of this article is ground 3b: whether the Government ‘erred in law by failing to take account of the effect of the project on greenhouse gas emissions between now and 2050, in the light of the government's obligations under the Paris Agreement and the Climate Change Act 2008’.[8][8] The applicant relied heavily on the reasoning in Plan B that the UK’s commitments under the Paris Agreement to have net zero emissions of greenhouse gases by 2050 was an obviously material consideration that the Secretary of State had failed to consider when deciding to designate the Airports National Policy Statement (ANPS).[9][9] The central concern was whether the Oakervee review adequately explained how the impacts of HS2 on UK greenhouse gas emissions sat with the Paris Agreement.

The Court of Appeal started by explaining the scope of the decision in Plan B. The court clarified that the decision was based on remedying four separate, but interrelated errors of law. S10(3)(a) of the Planning Act 2008 requires the Secretary of State to have regard to the ‘desirability of…mitigating, and adapting to, climate change’.[10][10] The only consideration under this issue was that the Paris Agreement, as an unincorporated international obligation, was obviously material to the decision to designate the ANPS on the facts of Plan B, in light of the Secretary of State's obligation in s10(3)(a). This conclusion ‘did not depend on the Government's commitment to the Paris Agreement necessarily having the status of “government policy” on climate change within the reach of section 5(8)’.[11][11] 

The circumstances of Plan B were very different to Packham and thus the reasoning in Plan B could not aid the claimant’s plight for three central reasons. First, the Oakervee review was not mandated under a statutory scheme, such as the Planning Act 2008, that shapes the decision-making process. As a result, the government was free to define the scope of the review and the issues it wished to be advised on.[12][12] Second, the advice in the review was ‘legally impeccable’ and dealt ‘amply’ with the emissions that would result from the construction of HS2; the impact of that on the Government’s 2050 target; and increase carbon efficiency may be improved in the construction process.[13][13] Finally, the government made its decision on the basis of legally sound advice, and, given the lack of evidence to the contrary, it could ‘be taken to have been fully aware of the United Kingdom's commitments under the Paris Agreement, and its own responsibilities under the Climate Change Act, and to have taken those commitments and responsibilities into account’.[14][14] 

The way that the court distinguished Plan B in this instance operates to emphasise how narrow that judgment was in the first place. Plan B did not lead to the conclusion that ‘as an unincorporated international obligation the Paris Agreement was automatically an “obviously material” consideration in any decision where the implications of infrastructure development for climate change were in issue’.[15][15] Rather, in certain specific statutory or factual contexts it has the potential to qualify as such. This suggests that relying on obligations under the Paris Agreement as a broad mechanism for challenging government decisions is unlikely to herald much success. This is particularly pertinent given how careful the judiciary were to emphasise the limited nature of the Plan B decision when it was delivered, holding that ‘we have not decided, and could not decide, that there will be no third runway at Heathrow’, or that such a plan would necessarily be incompatible with the UK’s political commitments on climate change.[16][16]

This cautious approach towards matters of political significance was reiterated in Packham. The court was keen to emphasise they would not pass judgment on the merits of HS2: ‘[t]hat is the government's responsibility, not the court’s’.[17][17] Thus, the court needed to afford the decision-maker a ‘broad margin of discretion’[18][18] in light of the ‘essentially political quality of the decision’[19][19].  Mr Packham’s challenge only required low intensity review based on Wednesbury irrationality and failure to consider obviously material considerations.[20][20] On the facts, there were no grounds to decide that the decision was irrational. 

This was also an unusual case because the HS2 project had been authorised by the High Speed Rail (London - West Midlands) Act 2017, which was still in force at the time of the Oakervee review. There seems to be an implicit recognition by the Court of Appeal that there may be issues with parliamentary sovereignty for an Act of Parliament to face being overturned by a review carried out by the executive.[21][21] The court noted that that 2017 Act will remain in force ‘regardless of the outcome of these proceedings’.[22][22] The court was also careful to indicate the scale of the claim being made: the challenge was to the government’s decision to proceed with HS2 project as a whole. These factors may have contributed to the reluctance of the courts to involve themselves with such a politically sensitive issue. 



This light-touch approach is reflected in R. (on the application of ClientEarth) v Secretary of State for Business, Energy and Industrial Strategy,[23][23] a recent decision of the High Court challenging the Secretary of State’s decision to uphold the grant of a development consent order for the construction of Europe’s largest gas plant, despite the government’s own planning authority recommending the plans be rejected on climate change grounds on climate change grounds. The court once again showed reticence in declining to interfere with the politically sensitive balancing process undertaken by the Secretary of State. The Secretary of State disagreed with the panel’s evaluation of the benefits of the proposal under section 104(7), including its contribution towards meeting policy needs. After weighing up those benefits herself she found that the impact of greenhouse gas emissions should not ‘carry determinative weight in the overall planning balance’.[24][24] These were matters for her planning judgment which the court would not interfere with.



It is perhaps a fair criticism that some of these judicial review applications devote considerable time and resources trying to gain merits-based review of environmentally controversial infrastructure projects by the backdoor. These applications appear to be attempts to pinpoint and utilise procedural defects in the decision-making process to indirectly challenge the substance of a government decision. However, as shown from obiter dictum in Plan B and Packham, and in the decision in ClientEarth, the courts are very reluctant to wade into political territory. As a result, these cases perhaps do not progress campaigns against environmentally harmful developments in the way that may have been anticipated following Plan B.

Moreover, in ClientEarth the court openly expressed that part of the claim was ‘a barely disguised challenge to the merits of the policy’.[25][25] These kind of statements from the judiciary risk adding to the perception that judicial review is being abused to review the merits of a decision, which has arguably fuelled desire for reform of judicial review. As Amy Hemsworth has compellingly argued, this looks like ‘further reductions of access rather than claimant-friendly reforms’, which would further impede the possibility of challenging the government on environmentally controversial infrastructure projects.

Further, even if judicial review applications are successful, it will usually only result in the decision being quashed: the court will not prescribe what the decision should be except where quashing the decision admits of only one possible decision.[26][26] In Plan B the court was very clear that despite the relief granted, complying with the duty in section 5(8) ‘does not even require the executive to conform to its own policy commitments, simply to take them into account and explain how it has done so’.[27][27] The fact that the government is not challenging the Court of Appeal decision in Plan B is perhaps an indication that even in light of the requirement to consider the Paris Agreement, the government does not believe that the decision will interfere too heavily with the plans to expand Heathrow (although the fate of the expansion hangs in the balance post-COVID-19).

I briefly note a couple of suggestions about how Non-Governmental Organisations (NGOs) may consider approaching climate change litigation going forward. First, climate change campaigners could push for a merits-based review mechanism by an expert panel for specific environmental issues. In Australia a similar process existed under the Environment Protection and Biodiversity Conservation Act 1999, and Silbert has argued for its reintroduction.[28][28] As sensible as this proposal sounds, the traditional separation of powers model in the UK means there does not appear to be an appetite for something similar to be implemented here. The UK’s judiciary is largely required to refrain from substantive review of politically contentious issues as such review has traditionally been viewed as strictly in the realm of political accountability mechanisms, such as ministerial responsibility to Parliament.

In light of this, perhaps environmental campaigners could focus on utilising statutes at the pre-legislative stage. NGOs could push for Ministers to use their statutory powers such as in Regulation 63(4) of the Conservation of Habitats and Species Regulations 2017. They could mount pressure on ‘the competent authority’ to consider the opinion of the general public at the pre-legislative stage and use their resources to educate and engage public opinion on a proposal before it becomes law.

A final thought is that perhaps the very purpose of climate change litigation ought to be reconceptualised. Fisher, Scotford and Barritt note that climate change litigation is ‘disruptive of adjudication’ because it often raises ‘questions about the legitimacy and limits of adjudication’.[29][29] They go on to suggest that climate change litigation could be understood ‘in terms of an expository justice model of adjudication’, where cases are less about who “wins” the dispute.[30][30] More important is the exposition of community values, expectations, and the specific role of different actors within the architecture of the state when it comes to solving what Fisher terms as ‘hot’ legal issues.[31][31] On this analysis, perhaps Packham and ClientEarth ought to be reimagined: not as failed attempts at using procedural defects to obtain substantive results, but as opportunities to expose the current balance of power in relation to climate change issues and highlight the importance that the community places on environmentally controversial infrastructure projects. The whole architecture of the state should be utilised to encourage a culture that prioritises environmental issues.



[1][1]  R. (on the application of Plan B Earth) v Secretary of State for Transport [2020] EWCA Civ 214

[2][2] [2020] EWCA Civ 1004

[3][3] Packham v Secretary of State for Transport [2020] EWHC 829 (Admin), [19]

[4][4] R (on the application of Packham) [2020] EWCA Civ 1004, [11].

[5][5] ibid, [67]

[6][6] ibid, [71]

[7][7] Ibid, [79].

[8][8] Ibid, [11]

[9][9] R. (on the application of Plan B Earth) v Secretary of State for Transport [2020] EWCA Civ 214, [98].

[10][10] Planning Act 2008, s10(3)(a)

[11][11] R (on the application of Packham) [2020] EWCA Civ 1004, [102]

[12][12] ibid, [103]

[13][13] ibid

[14][14] ibid.

[15][15] ibid [102].

[16][16] R. (on the application of Plan B Earth) v Secretary of State for Transport [2020] EWCA Civ 214, [285].

[17][17] [17][17] R (on the application of Packham) [2020] EWCA Civ 1004[4].

[18][18] Ibid, [51]

[19][19] Ibid, [53]

[20][20] Ibid, [48]

[21][21] Ibid, [52]

[22][22] Ibid, [52]

[23][23] [2020] EWHC 1303 (Admin).

[24][24] ibid [167].

[25][25] Ibid, [132]

[26][26] Civil Procedure Rules, Part 54, Rule 54.19

[27][27] R. (on the application of Plan B Earth) v Secretary of State for Transport [2020] EWCA Civ 214, [231].

[28][28] N Silbert, Challenging Decisions: Environmental Non-government Organisations’ Use of Judicial Review under the Environment Protection and Biodiversity Conservation Act 1999’ (Cth) (2018) 35 EPLJ 714, 732-733

[29][29] Fisher, Scotford and Barritt, ‘The Legally Disruptive Nature of Climate Change’ (2017) 80(2) MLR 173, 174-5.

[30][30] ibid, 197-8

[31][31] E Fisher, ‘Environmental Law as ‘Hot’ Law’’ (2013) 25 JEL 347