The law of belligerent occupation permits the Occupying Power to administer and use the natural resources in the occupied territory under the rules of usufruct. This provision has no counterpart in the provisions of humanitarian law applicable to non-international armed conflicts, which may suggest that any exploitation of natural resources by non-State armed groups is illegal. The International Committee of the Red Cross's updated 2020 Guidelines on the Protection of the Environment in Armed Conflict did not touch on this issue, and nor did the International Law Commission in its 2022 Draft Principles on the Protection of the Environment in Relation to Armed Conflicts, where it applied the notion of sustainable use of natural resources instead of usufruct. The present paper aims to fill this gap. It first reviews the development of the concept of usufruct and then studies whether the current international law entitles non-State armed groups with de facto control over a territory to exploit natural resources. By delving into the proposals raised by some commentators to justify such exploitation for the purpose of administering the daily life of civilian populations, the paper advocates for a limited version of this formula as the appropriate lex ferenda. In the final section, the paper discusses how situations of disaster, as circumstances which may preclude the wrongfulness of the act, may justify the exploitation of natural resources by non-State armed groups in the current international legal order.