“A la moindre escarmouche…” The Use of Force in Modern International Law: The Case of the DRC-Rwanda
“At the slightest skirmish, if they kill a Congolese citizen or seize another locality in Congo, I will convene both chambers in Congress, as required by the Constitution, and I will ask for authorisation to declare war on Rwanda.”
— President Félix Tshisekedi, 27 May 2025
Tensions in the Democratic Republic of the Congo (DRC) have reached a breaking point. President Félix Tshisekedi’s warning above came amid the rapid rise of the Alliance Fleuve Congo (AFC), a politico-military coalition formed in December 2023 and closely aligned with the M23 rebel group, active in eastern DRC since 2012. Their recent offensives have led to the capture of several strategic cities, including Goma and Bukavu, by early 2025.
While this conflict may appear internal, it carries significant international dimensions. Multiple UN reports, NGOs, and Western governments have accused Rwanda of providing direct support to M23 and the AFC, including allegations of Rwandan troops taking part in operations and offering strategic guidance. Kigali denies these claims, insisting its involvement aims solely to counter hostile groups operating from Congolese territory, such as the FDLR.
Amid escalating tensions, Tshisekedi’s statement raises a central question:
To what extent would a direct use of force by the DRC against Rwanda be lawful under international law?
Legal and Strategic Framework for the DRC’s Response
Modern international law is built on a strict prohibition of the use of force, enshrined in Article 2(4) of the UN Charter, a rule recognised as a peremptory norm (jus cogens). States are obligated to refrain from any threat or use of force against the territorial integrity or political independence of another state.
However, this does not amount to an absolute ban on all military action. International law recognises two main exceptions:
Self-defence (Article 51 UN Charter) — A state may use force in response to an armed attack when no other means of protection are available. To qualify, the attack must reach a certain threshold of scale and effects.
Collective action authorised by the UN Security Council (Chapter VII UN Charter) — The Security Council can adopt binding measures, including authorising the use of force, if it determines the existence of a threat to international peace and security. This could include revising or strengthening MONUSCO’s mandate or authorising targeted military action.
These are the only recognised legal avenues for the DRC to respond militarily to threats on its territory.
Legal Constraints on Using Force Against Rwanda
Despite these mechanisms, a crucial legal obstacle stands in the way of Tshisekedi’s proposed action: the principle of legitimacy.
Under international law, the classification of the conflict matters. Armed conflicts are either:
International armed conflicts (IACs) — between states
Non-international armed conflicts (NIACs) — between a state and non-state armed groups
Self-defence applies only in the context of an IAC, which requires the involvement of state actors. For the DRC to lawfully invoke self-defence against Rwanda, it must first establish Rwanda’s state responsibility by proving that Rwanda exercises effective control over the M23/AFC (ICJ Nicaragua case; ICJ DRC v Uganda case).
This means showing that Rwanda directly plans, commands, and supervises the group’s military operations, not merely supplying weapons, funding, or logistical support, however extensive.
The Evidence and Its Limits
While numerous reports and investigations have pointed to Rwandan support for M23 and the AFC, the evidence has yet to conclusively prove effective control. Without this, international law does not permit classifying the conflict as an IAC — and thus does not allow the DRC to lawfully use force against Rwanda under the doctrine of self-defence.
Therefore, even as the diplomatic and security context shifts in Kinshasa’s favour, the direct use of force against Rwanda remains legally contentious. Any unilateral military action could be viewed as illegitimate and in violation of international law.
Conclusion
President Tshisekedi’s declaration reflects mounting frustration and the urgent security realities on the ground. Yet, under the current international legal framework, the DRC faces significant constraints. Unless it can prove Rwanda’s effective control over M23/AFC or obtain UN Security Council authorisation, a direct military response against Rwanda would risk breaching international law.
Legal pathways remain, but they require diplomatic evidence-building, international consensus, and legal precision, not unilateral escalation.
