JOHN THYS/AFP via Getty ImagesThe world’s highest court says countries are legally obliged to prevent harms caused by climate change, in a ruling that repudiates Australia’s claims it is not legally responsible for emissions from our fossil fuel exports.The landmark ruling overnight by the International Court of Justice (ICJ) will reverberate in courts, parliaments and boardrooms the world over.In a closely watched case at The Hague, the judges were asked to clarify the legal obligations countries have to protect the Earth’s climate system for current and future generations. They were also asked to clarify the legal consequences for nations that fail to do this.At issue was the scope of legal obligations. During the court’s deliberations, Australia sided with other fossil fuel exporters and major emitters – including Saudi Arabia, the United States and China – to argue state obligations on climate change are restricted to those set out in climate-specific treaties such as the Paris Agreement. But the court disagreed. It found countries have additional obligations to protect the climate and take action to prevent climate harm inside and outside their boundaries. These obligations arise in human rights law, the law of the sea, and general principles of international law. This clear statement will have groundbreaking consequences. It means Australia must set a 2035 emissions reduction target in line with the best available science, as required under the Paris Agreement. But it must also go further, by regulating the fossil fuel industry to prevent further harm. Australia’s arguments rejectedThe ICJ is the primary legal organ of the United Nations. Its key role is to settle disputes between countries and clarify international law as it applies to nation states.While weighing up the obligations of countries to address the climate crisis, the court heard legal arguments from almost 100 countries, making it the largest case ever heard by the ICJ.The case threatened major implications for fossil-fuel producers such as Australia, which is heavily reliant on coal and gas exports.In his oral presentation to the ICJ, Australian Solicitor-General Stephen Donaghue told the court only the Paris Agreement should apply when it comes to mitigating climate change. Under the Paris rules, countries must set targets to cut domestic emissions, but they are not required to report emissions created when their fossil fuel exports are burned overseas. Donaghue and the Australian delegation also suggested responsibility for harms caused by climate change could not be pinned on individual states. Australia also argued protecting human rights does not extend to obligations to tackle climate change.The ICJ largely rejected these arguments. The ICJ judges largely rejected Australia’s arguments. Pictured: ICJ President Yuji Iwasawa (third from right) and members issuing their advisory opinion. JOHN THYS/AFP via Getty Images Fossil fuel era is overThe court found Australia, and other fossil fuel producers, are obliged under international law to prevent fossil fuel companies in their territory from causing significant climate harm. This will essentially require a managed phase out of fossil fuel production. As the ICJ ruling says:Failure of a State to take appropriate action to protect the climate system from [greenhouse gas] 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 which is attributable to that State. Australia is one of the world’s largest exporters of coal and gas. When burned overseas, emissions from Australia’s fossil fuel exports are more than double those of its entire domestic economy.Australia has approved hundreds of oil, gas and coal projects in recent decades. Dozens more are in the approvals pipeline. Final federal approval is still pending for Woodside’s massive Northwest Shelf gas project – which is set to add millions of tonnes of greenhouse gas emissions every year, for decades.The Australian government must heed the message from the Hague. The days of impunity for the fossil fuel industry are coming to an end. Woodside’s massive Northwest Shelf gas project is set to add millions of tonnes of greenhouse gas emissions every year. GREG WOOD/AFP via Getty Images A spark of hope from the PacificToday’s ruling is remarkable for where it originated. In 2019, 27 law students at the University of the South Pacific in Vanuatu were given a challenge: find the most ambitious legal pathways towards climate justice. Each year, Vanuatu faces the prospect of cyclones, earthquakes, tsunamis, volcanoes, flooding rain and drought. Climate change compounds the risk to island communities – people who have done the least to contribute to the problem. The students decided to file a case with the world court. And so began a legal campaign that travelled from Vanuatu’s capital, Port Vila, through the halls of the United Nations in New York and to the world court in the Hague. In 2023 Vanuatu and other island nations succeeded in passing a UN General Assembly resolution. It asked the ICJ to give an advisory opinion on countries’ obligations to protect the climate system and legal consequences for states causing “significant harm” to Earth’s climate.This week’s ruling delivers poetic justice to Vanuatu and other vulnerable island states. The ruling delivers poetic justice to Vanuatu and other vulnerable island states. Pictured: representatives of Pacific states outside the International Court of Justice in December 2024. Michel Porro/Getty Images A new era for climate justiceThe court’s findings are likely to influence a wave of climate litigation worldwide. It could shape legal reasoning in Australia, too. Last week, a Federal Court judge found the Australian government has no legal duty of care to protect Torres Strait Islanders from climate change. If that case is appealed, a superior court may revisit the government’s obligations – and have regard to the ICJ ruling in doing so.The ICJ decision will also be relevant for the Queensland Land Court, which this week began hearing a challenge to stop a greenfield mine proposed by Whitehaven Coal – citing environmental and human rights impacts of the project’s emissions. Clarified international law obligations should also guide policymakers in the Australian parliament. With a huge majority in the House of Representatives and a climate-friendly Senate crossbench, the Albanese government has a mandate to implement policy in line with Australia’s international law obligations.Wesley Morgan is a fellow with the Climate Council of AustraliaGillian Moon is a regular donor to the Australian Conservation Foundation, which is a party in the Whitehaven Coal case.