Regulating Military Force Series – Introduction

by , , | Feb 20, 2024


In 1970, Professor Thomas Franck boldly concluded that only 25 years after the adoption of the UN Charter, Article 2(4) had been killed by the very States that had created it. In the 50 years since this conclusion, assaults on Article 2(4) and further aspersions on its effectiveness have been made. Given repeated, sometimes nominal, sometimes massive violations of the prohibition, there is little wonder why its continued relevance is questioned (see more recently here, here, and here).

It is in this light that the Centre for International Humanitarian and Operational Law at the Palacký University in Olomouc, Czech Republic, hosted a conference on the theme of the regulation of resort to force in international law, exploring the perpetually strained prohibition on the use of force. In that same light, we introduce this Articles of War series and provide some opening thoughts.

Assessing the Jus ad Bellum

Although already apparent in the 20th century, doubt concerning the efficacy of the jus ad bellum has been a defining feature of the 21st century security environment. The September 11 terrorist attacks by al Qaeda and the subsequent U.S.-led invasions of Afghanistan in 2001 and Iraq in 2003 paved a turbulent path. Events that followed those two large-scale collective resorts to force only confirmed Franck’s fears. The Great African War in the Congo (the deadliest conflict since the Second World War), coalition interventions in Syria, recurring military action in Lebanon and Gaza, and Russia’s intervention in Georgia to name only a select few have provided ample grist for the mill of jus ad bellum skepticism. Had these situations not shaken the effectiveness of the prohibition by the end of the century’s first decade, the purported annexation of Crimea in 2014 and the full-scale invasion of Ukraine in 2022 surely seemed to tear into its core.

These conflicts have not only strained the standing of the jus ad bellum regime as a legal and practical deterrent to the resort to force. They have demanded new interrogations of pre-existing doctrinal assumptions and debates and given rise to new ones including: the right of pre-emptive self-defense; implications of the use of force against non-State actors; and implicit, post-facto and revived Security Council authorizations.

And although the 1990s saw sporadic and furtive progress on UN efforts at addressing matters of international peace and security, by the second decade of the 21st century, the Security Council has become a shadow of its former, short-lived self. Disagreements among Member States and regular use of the veto by the permanent five (most notably by Russia, China and the United States) have hamstrung the Council’s ability to effectively address a number of dire situations, including those in Ukraine, Palestine, Syria, and Yemen.

The Prognosis for Relevance

Be that as it may, violations of the jus ad bellum regime may also have highlighted the need for its continued existence. For each seemingly mortal blow to the prohibition, an equally powerful attempt at resuscitation has followed. Most recently, for example, the landmark UN General Assembly Resolution ES-11/1 on aggression against Ukraine recalled all States’ obligations under Article 2 of the UN Charter prohibiting the use of force and deplored Russia’s violation of Article 2(4) in Ukraine. The resolution was adopted with an overwhelming 141 votes in favor. Such reaffirmations confirm that Article 2(4), and the broader system of collective security, despite their flaws, remain as relevant to the legal and political calculations of States today as they did some 75 years ago.

At its heart, the modern jus ad bellum reflects an understanding that States’ authority to pursue their individual interests by armed force, as a constant source of instability in the international community, must be regulated and bolstered by a collective system of peace enforcement. The jus ad bellum thus simultaneously understands both peace and security as values common to the entire international community. They are reflected respectively in the collectivization and institutionalization of peace enforcement and preservation of the right of self-defense. Of course, herein lies the inherent tension, and perhaps fatal flaw, of the jus ad bellum recognized by Professor Franck and others long ago.

That tension featured prominently during the conference and will be a recurring theme in this series. While the UN Charter and customary international law are not challenged as to their existence, their practical relevance and indeterminacy receive highly critical attention. Several posts illustrate how the jus ad bellum seeks to narrow the room for legal and political maneuvering by States. But they will highlight how this narrowing function has inspired States to adopt broad, and at times even spurious, interpretations to justify their conduct. These interpretations not only call into question the function of international law as a social tool, but also expose a dissociation between States’ security needs and the international law security model (especially the recognized need for Security Council reform).

Concluding Thoughts

Appeals for an overhaul of the jus ad bellum regime and the UN Charter system of collective security may well be founded. Yet, they often neglect the fact that international law, and perhaps especially the jus ad bellum, are far less susceptible to revolutionary change than other legal regimes. It is therefore likely that through evolutionary, rather than revolutionary steps, the jus ad bellum prohibition on the use of force will cling to life. Just as with respect to the conference, we hope this series proves an informative and productive effort to identify doctrinal and political common ground for this most fraught, yet fundamental regime of international law.


Martin Faix is Head of the Centre for International Humanitarian and Operational law and the Vice-Dean for International Affairs of the Faculty of Law, Palacký University.

Marko Svicevic is a Lecturer and Researcher at the Centre for International Humanitarian and Operational Law, Faculty of Law, Palacký University in Olomouc, the Czech Republic.

Sean Watts is a Professor in the Department of Law at the United States Military Academy, Co-Director of the Lieber Institute for Law and Land Warfare at West Point, and Co-Editor-in-Chief of Articles of War.



Photo credit: Staff Sgt. Jacob Sawyer