A landmark outcome from the International Court of Justice (ICJ) on 23 July found that countries have an obligation to contribute to cutting emissions, and wealthy, industrialised nations should take the lead on tackling climate change. The court left the door open for further climate litigation, finding that breaching these obligations constitutes a "wrongful act" for which "injured states" could claim restitution and compensation.

The ICJ's advisory opinions are not legally binding but carry significant weight and may contribute to the development of international law, non-profit the Centre for International Environmental Law says. International climate treaties — such as the 2015 Paris Agreement — "establish stringent obligations upon states to ensure the protection of the climate system and other parts of the environment from anthropogenic GHG [greenhouse gas] emissions", the ICJ said.

Countries "must fulfil their duty to prevent significant harm to the environment by acting with due diligence", the ICJ said. It noted the discretion built into UN climate body the UNFCCC for nations to determine the means by which they cut emissions. But it was clear that "this discretion cannot serve as an excuse for states to refrain from co-operating with the required level of due diligence or to present their effort as an entirely voluntary contribution which cannot be subjected to scrutiny". The court found that countries party to the Paris Agreement have an obligation to present national climate plans that align with its primary temperature goal of limiting the global rise to 1.5°C from a pre-industrial baseline.

The ICJ also focused on the primary cause of GHG emissions — burning fossil fuels. "Failure of a state to take appropriate action to protect the climate system from GHG emissions — including through fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licences or the provision of fossil fuel subsidies — may constitute an internationally wrongful act... attributable to that state", it found. "Where several states are responsible for the same internationally wrongful act, the responsibility of each state may be invoked," it said.

Definitive legal guidance

The ICJ's opinion "will equip judges with definitive guidance that will likely shape climate cases for decades to come", environmental organisation ClientEarth lawyer Lea Main-Klingst previously told Argus. Existing pathways could allow countries to take legal action against other nations, "and no changes to international law are needed for it to happen", CIEL climate and energy programme director Nikki Reisch tells Argus.

Individual states could vary in how they interpret the court's findings, but the opinion was comprehensive and punctured arguments often used to push back on more stringent climate action.

The ICJ noted that "it is scientifically possible to determine each state's total contribution to global emissions, taking into account both historical and current emissions", and that states could be found responsible if they do not regulate emissions caused by "private actors" under their jurisdictions.

Climate litigation has risen steadily in recent years and cases including those challenging fossil fuel projects are "more often reaching the highest courts around the world", researchers at the London School of Economics' Grantham Research Institute say. And the damage caused by climate change is growing, increasing the pressure to define legal parameters and responsibilities.

The ICJ proceedings hit several milestones. The issue drew the highest level of participation in a proceeding seen by the ICJ or its predecessor. And the court adopted the advisory opinion unanimously — just the fifth time in its 80-year history that this has happened. But it made the point that international law is just one tool in the fight against climate change. The proceedings "concern an existential problem of planetary proportions", the ICJ said. "International law… has an important but ultimately limited role in resolving this problem".

By Georgia Gratton