In September 2011, the President of Palau made a statement to the UN General Assembly in which he asked the General Assembly to “seek, on an urgent basis… an advisory opinion from the International Court of Justice on the responsibilities of States under international law to ensure that activities carried out under their jurisdiction or control that emit greenhouse gases do not damage other States”. While the question eventually submitted to the Court is still under negotiation, the ‘no-harm rule’ or ‘principle of prevention’ is, provided the initiative goes ahead, likely to form an integral part of the legal analysis.

The no-harm rule is a widely recognised principle of customary international law whereby a State is duty-bound to prevent, reduce and control the risk of environmental harm to other states. This paper provides a short analysis of the potential application of this obligation in the context of climate change. It will not explore other related legal issues such as the attribution of damages, the standard of proof or the relationship between the United Nations Framework Convention on Climate Change (UNFCCC) and other rules of public international law.