On 14 and 15 September 2023, the Centre for International Humanitarian and Operational Law hosted its much-anticipated conference: International Law and the Regulation of Resort to Force: Exhaustion, Destruction, Rebirth? Bringing together an assembly of some 70 experts, scholars and practitioners from across the world, the conference explored the intricate and ever-stretched prohibition of the use of military force in international law. Contributors explored a wide array of subjects, including the jus ad bellum regime, the relationship between the prohibition and its exceptions, the prohibition of force as a peremptory norm in international law, hybrid warfare, the need for UN Security Council reform and the interpretation of its resolutions, humanitarian intervention and the responsibility to protect doctrine, as well as the nuanced landscapes of individual and collective self-defence. Moreover, the role of cyber operations, the intersection of force with issues of territory, human rights and international humanitarian law, and the use of force by international organisations were also central topics of discussion.

Some of the key outcomes of discussions and engagements during the two-day conference included:

The Prohibition of Force, the UN Charter System of Collective Security and the Right of Self-Defence

• Despite the continued pressure on Article 2(4), the prohibition of the use of force remains resilient. Its continued violation by States, rather than weaking the prohibition, reaffirms its relevance and importance in international relations.
• Where collective security under the Charter of the United Nations concerns, including the role of the UN Security Council, a number of factors which contributed to the demise of the League of Nations threaten also the future of the UN Security Council.
  • Ambivalent legal bases which have previously been used to justify military operations, such as the discussions on whether Article 42 or Article 51 form the legal basis for Council’s authorisation of enforcement action.
  • Abusive interpretations of UN Security Council mandates, which sometimes go beyond what has been permitted by resolutions.
  • An ever-increasing reliance on self-defence as a basis for military action: The interpretation of UNSC Resolution 2249 (2015) as providing States with a right to invoke self-defence against ISIS/ISIL, when the right of self-defence in fact requires no UN Security Council authorisation.
  • The above-mentioned issues have a two-fold approach to collective security: first, there is a backlash against the UN Security Council’s ability to use Chapter VII measures – that is, these resolutions are difficult to adopt given that they may be abusively interpreted in favour of authorisation of the use of force. Second, where the UN Security Council invokes other legal bases for the use of force (such as self-defence), it is in fact involved in its own demise by abdicating its primary responsibility for the maintenance of international peace and security under Article 24 of the UN Charter.
• Past precedents have set the stage for repeated abuses of international law prohibiting force. Both States and regional organisations may in turn see this as a justification to make use of their own treaty instruments to use force, without necessarily adhering to the UN Charter provisions on collective security.

Recurring Issues

• The rise of cyber and digital technology has brought about challenges to the legal landscape regulating the use of force. Existing international legal frameworks need to be flexible and evolve continuously to meet demanding challenges.
• Private military and security companies (PMSCs), although not novel in times of armed conflict, continue to play a growing role, as evidenced recently by their use in the aggression against Ukraine.
• Continued reliance on debatable exceptions to Article 2(4), such as those of Responsibility to Protect and Humanitarian Intervention, ultimately increase the prohibition’s vulnerabilities to erosion and non-compliance.
• Although firmly established in international law, the prohibition of the use of force to acquire territory has recently resurfaced, particularly through the actions of the Russian Federation.
• Abusive interpretations of exceptions, in particular that of the right of self-defence, has directly impacted the strength of the prohibition of the use of force, and corroded the very relationship between the prohibition and exceptions to it.