Symposium on International Conflict and Security Law: A Research Handbook – Use of Force, Veto Use at the UN Security Council, and the Crime of Aggression

[Jennifer Trahan is a Clinical Professor at NYU’s Center for Global Affairs and Director of their Concentration in International Law and Human Rights. She serves as Convenor of the Global Institute for the Prevention of Aggression where Annegret Hartig is Program Manager, and Sergey Sayapin is on the Council of Advisors.]

The editors, Sergey Sayapin, Rustam Atadjanov, Umesh Kadam, Gerhard Kemp, Nicolás Zambrana-Tévar, and Noëlle Quénivet, deserve praise for gathering together so many important contributions related to international peace and security. This post focuses on chapter 6 on the use of force, chapter 7 on the UN Security Council, and chapter 50 on the crime of aggression.

Chapter 6: The Use of Force in International Law by Onder Bakircioglu

This chapter starts by tracing the early attempts to regulate international peace and security (use of force) through what has become the jus ad bellum regime. It commences with a brief discussion of use of force doctrine prior to the 1900s when States were largely left to decide for themselves when to have recourse to the use force. The chapter then traces the development of the League of Nations and its contribution toward outlawing aggressive war by mandating amicable settlement of disputes and a three month “cooling off period” before states could go to war. The Covenant of the League of Nations also created a Council of the League of Nations as well as a sanctions regime.

The chapter then covers the transformative moment in 1928 with the conclusion of the first multilateral treaty outlawing aggressive war:  the Kellogg-Briand Pact, officially known as the General Treaty for Renunciation of War as an Instrument of National Policy, which was ultimately acceded to by sixty-three states by 1938. 

While all readers will know of the failure of both the League and Pact in the events leading up to, and, including World War II—particularly the lack of enforcement powers—the chapter illustrates how these instruments contributed to what became the basic framework in the UN Charter for regulating the use of force.  Through these three core texts one thus sees a seismic shift: the eventual recognition that, given the cataclysmic destruction wrought by two world wars, it had become imperative to prevent aggressive war (use of force) through the rule of law.
While not all that is contained in the chapter is new (some of the same territory is covered, for example, in Oona Hathaway and Scott Shapiro’s book, The Internationalists), the background is central to understanding the use of force regime in the Charter and the book would be incomplete without it.  

The chapter additionally examines some open questions—what one might call “grey areas”—in the Charter regime and customary international law, particularly related to the doctrine of self-defense. It also briefly wraps in challenges posed to the doctrine of self-defense in the aftermath of 9/11—which is such an extensive topic that it could have warranted its own chapter (or book). The chapter ends with an important plea to remain vigilant against attempts to water down the jus ad bellum regime embodied in customary international law and the UN Charter.

Two criticisms. First, while the chapter acknowledges the problem of veto use by permanent members of the UN Security Council paralyzing that body, even in situations that fall under the “responsibility to protect” (“R2P”) doctrine, the chapter does no more than reflect the existence of the problem (p. 131). Yet, such vetoes can be central to the failure of the peace and security architecture of the UN Charter. There are some who propose potential solutions to that paralysis (or a way to start chipping away at it). I write about this in my book, Existing Legal Limits to Security Council Veto Power in the Face of Atrocity Crimes (CUP 2020). There, I argue that states need to question the legality of vetoes when they block the Council from acting to prevent or stop the commission of genocide, war crimes or crimes against humanity. I suggest one way to do so would be for the General Assembly to seek an Advisory Opinion on the topic from the International Court of Justice (“ICJ”), an idea that has now been taken up in resolutions of the Council of Europe (see, e.g., res. 2482 (2023), para. 23).

Second, there is only one scant reference to a war of aggression being a “crime against peace” (p. 125)—what is now referred to as the crime of aggression. For discussion of enforcement of the UN Charter system though the regime of individual criminal responsibility one has to wait until Annegret Hartig’s chapter, chapter 50.  Nor is there any cross-reference to suggest that individual criminal responsibility for the crime of aggression is one way to enforce the use of force regime within the UN Charter.

Chapter 7: The UN Security Council by Rossana Deplano

Rossana Deplano’s chapter, chapter 7, also recognizes the problem of veto use, or failure to pursue resolutions where a direct interest of a permanent member is at issue. She, for example, notes Security Council paralysis related to Tibet, Chechnya, Syria, and the Russian annexation of Crimea (p. 154). Today, we could, of course, add the Russian invasion of Ukraine and Russia’s recent illegal attempts at annexation.  Her chapter, while noting that jus cogens may provide legal limits to the Security Council’s powers (p. 150), also does not suggest a direct way to challenge such Security Council paralysis.

The chapter does, however, provide an interesting and intricate content analysis of the Security Council’s 2,369 country-specific and thematic resolutions adopted between 1946 and 2017, analyzing the extent to which they invoke international law.  She concludes that by doing so “the Security Council is slowly, but relentlessly, moving from protecting state sovereignty only to protecting humanity. . . .” (p. 168). That may be the case—but arguably only when a permanent member is not using its veto to block those attempts—and one might well ask how many lives will be lost while the Security Council is slowly making progress by invoking international law. My ideas, including a legal challenge brought to the ICJ in the form of a request for an advisory opinion would tee up the issue more directly. 

Chapter 50: The Crime of Aggression by Annegret Hartig

Returning to the missing linkage between Chapters 6 and 50, while this may seem a slight omission, the connection seems necessary. The key moments in the development of jus ad bellum flow directly into the efforts to enforce that regime through individual criminal responsibility. This of course famously happened with the prosecutions before the International Military Tribunals at Nuremberg and Tokyo (and subsequent trials in both locations). Another key development was the decision in 1998 to include the crime of aggression as one of the core crimes in the Rome Statute of the International Criminal Court. As Hartig traces in her chapter, later significant developments include the 2010 decision to complete the Rome Statute through the Kampala amendments on the crime of aggression (which was preceded by nearly a decade of negotiations within the Court’s Special Working Group on the Crime of Aggression) and the ICC Assembly of State Parties’ 2017 decision to activate the ICC’s jurisdiction over the crime effective in 2018. 

Hartig’s chapter also contains an interesting discussion of why, in the Nuremberg Judgment, the crime of aggression is called “the supreme crime, differing only from other war crimes in that it contains within itself the accumulated evil of the whole.” To this author the answer seems obvious that if aggression is not committed, then all the other crimes (as well as other fatalities) during a war do not occur. That said, I’ve never thought it was particularly useful to have a hierarchy of crimes, as gravity is certainly somewhat context dependent. In addition to other possible explanations, Hartig suggests that perhaps the reality of World War II explains why the crime was labeled “the supreme crime” and that does jump out as an obvious explanation. Also, one must remember that the crime of genocide was not prosecuted at Nuremberg. Obviously, Hartig was writing before the 2022 invasion of Ukraine, but the gravity of the crimes and harms being inflicted there again suggest why the appellation “supreme crime” is certainly appropriate in that situation. 

My most significant complaint with the chapter is its dispiriting framing. The full title of the chapter is: The crime of aggression: the fall of the supreme international crime? My critique is admittedly somewhat unfair because the chapter was written well before Russia invaded Ukraine. At present, it does not at all feel as if the crime has “fallen” in stature; rather, the crime appears to have completely resurfaced as it is receiving more attention now than ever before. 

Hartig discusses the ICC’s jurisdiction over the crime and why it is different than that of the ICC’s other core crimes (pointing out the weakness in the crime of aggression’s jurisdictional regime under the ICC’s Rome Statute) (pp. 1117-1120). That is accurate, but there are now calls by both Parliamentarians for Global Action and the group I convene, the Global Institute for the Prevention of Aggression, to amend the crime’s jurisdictional regime. Under the 2010 Kampala amendments’ resolution, a review of the crime is slated to occur seven years after the crime’s activation; because activation occurred in 2018, the review is set for 2025. States Parties need to take up this issue urgently, as facilitation will be needed before then.

Hartig also gloomily reported only 13 states had implemented the Kampala definition of the crime of aggression into their domestic criminal codes (p. 1123); the number is now 15-16 (see Hartig’s new book, ch. 6). She failed, however, to include the approximately 40 additional states that had already implemented the crime into domestic legislation based on the Nuremberg Tribunal’s earlier definition (see Reisinger Coracini); thus, the total is around 55 states. While that is less than one might hope, many domestic criminal codes also lack crimes against humanity legislation (see here). 

Moreover, after the invasion of Ukraine, there are global calls for accountability for the crime of aggression being committed against Ukraine. One finds these in numerous resolutions (see, e.g., European Parliament res. 2022/3017(RSP), paras. F, P, Q; Council of Europe res. 2436 (2022), para. 11.6; the Parliamentary Assembly of NATO, para. 18j), entreaties by the Government of Ukraine as well as other states, and countless blog posts on the topic (see, e.g., here, here, and here). Whether a credible ad hoc tribunal to prosecute the crime can be created is too early to tell. (The Rome Statute amendment process is calculated to be complex and time-consuming, and likely could not be completed in time to cover the situation of Ukraine.)

Finally, Hartig examines a narrow but significant topic: Draft Article 7 of the study by the International Law Commission (“ILC”) of Immunity of State officials from foreign criminal jurisdiction. In it, the ILC left the crime of aggression off the list of crimes as to which they claim functional immunity does not attach. The ILC lists only genocide, crimes against humanity, war crimes, apartheid, torture, and enforced disappearances as not subject to functional immunity. Construing this omission, Hartig notes both the conservativism of the ILC (p. 1129) and division among ILC members on the topic, on which they failed to reach consensus and had to adopt the draft article by vote (p. 1128). Hartig is right to draw our attention to this topic and apparent flaw in the ILC’s work.

Hartig ends with a stirring call (p. 1132) that states not fragment the Rome Statute’s four crimes and stop leaving the crime of aggression off the list of “core crimes” or “atrocity crimes.” Sergey Sayapin (in chapter 22) also appropriately includes the crime of aggression as one of the ICC’s core crimes (p. 487). Hartig concludes with a reminder of the centrality of the crime during the Nuremberg prosecutions and warns that “[m]arginalizing the crime of aggression may thus destabilize the very foundations of international criminal law.”

Together, these three chapters cover much territory on the role of international law and the UN in contributing to the basic peace and security architecture of the international legal system.