The nonbinding nature of the commitments in the Paris climate change accord means that national legislatures have flexibility over how to combat climate change. In the absence of a binding multilateral agreement, citizens are holding national legislatures to account over their policies to reduce greenhouse gas ("GHG") emissions. Legal challenges have already been brought against the Dutch and Belgian governments by groups seeking to pressure them to commit to larger GHG emission reductions. The UK government is also being threatened with legal action.

In Urgenda v Kingdom of the Netherlands, a court in the Hague found in favor of 900 Dutch citizens who argued that the Dutch government's existing legislative commitment to reduce GHG emissions by 17 percent on 1990 levels by 2020 was insufficient to meet the requisite duty of care to the claimants. The Dutch government has appealed. A similar case in Belgium, VZW Klimaatzaak v Kingdom of Belgium, et al., is currently pending.

On September 29, 2017, Plan B, a charitable group supporting "strategic legal action" against climate change, launched judicial review proceedings with a pre-action letter that attacks the failure of the UK government to revise its 2050 carbon target under the UK Climate Change Act 2008.

Plan B alleges that the Secretary of State for Business, Energy, and Industrial Strategy's failure to make more ambitious targets for 2050 is beyond the scope of its authority, irrational, and a breach of fundamental human rights. The group further alleges that the UK government is wrong in its opinion that the target of the Paris accord to keep global warming under 1.5°C is "aspirational" rather than "essential." Tim Crosland, barrister, and director of Plan B, describes this view as "like a pilot saying, as his plane careers towards the mountainside, that he's not quite ready to change trajectory as he needs more time to study his map. It is not a reasonable or rational response to the situation."

Plan B seeks to force the Secretary of State to change the 2050 target to a more ambitious one in respect of GHG emission reduction targets. This challenge also aims to further strengthen cases of similar groups worldwide who seek to use legal action against governments as a way of protecting the environment. This will be the first case in the UK to directly tackle climate change targets set by the UK government, although climate change targets have been raised in a number of other judicial review cases. R (Hillingdon LBC) v Secretary of State for Transport concerned plans for a third runway at Heathrow and Derbyshire Dales District Council v Secretary of State for Communities and Local Government concerned a planning application for the installation of wind turbines. In Hillingdon the judge held that, in principle, statements concerning a government's commitment to climate change were subject to judicial review and in Derbyshire Dales the judge supported the effect upon climate change as a ground for a policy decision. The Plan B case will offer further insight into whether the UK courts will stray further into a politically sensitive area or hold back and defer to the UK Parliament.