Case law and practice: The challenge of enforcement

A central difficulty in operationalising the due regard principle is the absence of robust judicial interpretation, particularly from international courts, that gives the rule concrete legal contours during armed conflict. While the principle is widely recognised in customary IHL and reflected in military doctrine, courts have so far addressed environmental protection only indirectly, leaving significant ambiguity around how due regard should function in practice.

The Gabcíkovo-Nagymaros Project case remains one of the most frequently cited authorities for environmental due diligence obligations. Although not an armed-conflict case, the International Court of Justice (ICJ) affirmed that environmental protection constitutes an ‘essential interest’ of states and recognised a general obligation to integrate environmental considerations into all activities, particularly those involving scientific uncertainty. This emphasis on precaution and environmental risk management echoes core elements of the due regard principle, reinforcing the expectation that states must act proactively, even in uncertain conditions.

Similarly, in the Legality of the Threat or Use of Nuclear Weapons Advisory Opinion, the ICJ held that environmental considerations ‘are not an abstraction’ and must inform the application of IHL during hostilities. While the ICJ stopped short of defining a standalone environmental obligation, it acknowledged that environmental protection operates as a substantive constraint within IHL. This recognition provides important normative support for due regard, even if it does not clarify its precise legal threshold.

There are, however, some more recent developments worth noting. In its 2022 judgment in DRC v Uganda (Reparations), the ICJ awarded damages for environmental damage to fauna in a national park, recalling that compensation is due for damage caused to the environment in and of itself, and that damage to the environment and the consequent impairment or loss of the ability of the environment to provide goods and services is compensable under international law. While not directly adjudicating the due regard rule, this decision represents meaningful progress in recognising environmental harm as legally actionable in an armed-conflict context.

Ukraine has announced and is conducting ongoing investigations into ecocide and war crimes in relation to environmental damage, signalling growing state practice in this area. Additionally, the UN Compensation Commission (UNCC), established to process claims arising from Iraq’s actions during the 1990–91 Gulf War, made numerous awards for environmental damage resulting from the burning and spilling of Kuwaiti oil wells, prioritising ecological functioning as the objective of remediation and awarding compensation accordingly. These developments, while not definitive, gesture to a slowly evolving landscape.

Despite these touchpoints, the jurisprudence falls short of supplying an enforceable framework. No international tribunal has yet found a belligerent responsible for breaching environmental obligations during hostilities, even in cases involving major pollution events, oil-well fires, or widespread ecosystem degradation.