Variable 2: Use of Force

With the horror and devastation of the Second World War set to fade entirely from living memory over the coming years, the taboo on the use of large-scale aggressive force will continue to come under considerable strain. As the open invasion of Poland, the firebombing of Dresden, the siege of Leningrad, and the atomic strikes on Hiroshima and Nagasaki fade into the distant past, the temptation of war grows ever stronger and restraints on its conduct risk growing weaker.

…we are witnessing a trend of lax interpretations and implementation of international humanitarian law. Left unaddressed, civilians will experience even worse consequences in the future.

Interstate violence — from Ukraine to the Middle East to the Great Lakes region of Africa — is already becoming an increasingly salient feature of global politics. If U.S.-China tensions continue to mount, the South China Sea may be another addition to this list. The same is true of violence between states and non-state actors.

Moreover, we are witnessing a trend of lax interpretations and implementation of international humanitarian law (IHL). Left unaddressed, civilians will experience even worse consequences in the future. Protracted conflicts will continue to produce long-term instability and suffering, reducing the prospects for reconciliation and durable peace. While IHL may continue to be regularly invoked by name, the manifest lack of respect for it threatens its relevance and protective power.

What is more, the grounds of what constitutes self-defense have expanded over the past three decades. Under the guise of defending against terrorist organizations, the use of kinetic force has increased between countries that are not formally at war, often without the consent of the targeted state. While the great powers have primarily undertaken this invocation of self-defense, rising middle powers are increasingly modeling their behavior — and legal justifications — on such conduct. 

The double standards and recklessness on display today, repeatedly justified through alleged “non-precedents” or appeals to universal principles, have set de facto precedents. This has engendered a tit-for-tat process that continually erodes norms surrounding the use of force, both in respect of jus ad bellum and jus in bello.¹ The current conflicts in Gaza and Lebanon, which have led to a direct clash between Israel and Iran, reveal the dangerous escalatory potential of this dynamic, underlining the need to prevent lax justifications and behavior where military action is concerned.

Limiting the scourge of war

For more than 75 years, we have operated from the starting premise that it is forbidden to threaten or use force against the territorial integrity or political independence of a state unless specific restrictive criteria are met. The use of force is only permissible in self-defense or when authorized by the U.N. Security Council, never in retaliation or as revenge. It is unacceptable to let this commitment erode. To avoid a far more violent and unstable world, the international community must tighten and breathe new life into norms surrounding the use of force while reaffirming the U.N. Charter. Decisive and far-reaching (yet targeted) actions will be necessary to preserve the credibility and universal legitimacy of norms whose purpose is to limit interstate violence and uphold IHL, especially given the exponential multiplication of abuses that we will likely witness as a larger set of countries feel emboldened to skirt these norms and laws.

While it is the lack of adherence to law rather than the absence of law itself that lies at the heart of many transgressions, we recognize that further constraints are necessary to strengthen the likelihood of compliance.

Many other variables addressed in this project seek to constrain or impose agreed-upon limitations on interstate behavior, especially between great powers. This section of the report is limited to addressing other outstanding issues related to the use of force, such as exploring ways to restrict a particularly frequent justification for the use of force and to strengthen limits on the conduct of hostilities. In doing so, we aim to provide an added — and necessary — modicum of predictability to a changing international order. The proposed measures below, which aim to render select international norms more robust, remain compatible with the emergence of a more decentered or region-centric international order — and with a world in which the most influential countries agree to share power.

While it is the lack of adherence to law rather than the absence of law itself that lies at the heart of many transgressions, we recognize that further constraints are necessary to strengthen the likelihood of compliance, given that existing frameworks have failed to prevent the highly consequential violations witnessed to date. Pursuing the adoption of these constraints will become even more important in a world that increasingly features war against non-state actors and armed conflict at the interstate level.

Proposal 4: Reinforcing international humanitarian law

Recent conflicts, technological advances, and changes in the nature of warfare are fueling the proliferation of war in scale and scope. In response, this report advances three recommendations: developing a new additional protocol to the Geneva Conventions to codify a more detailed definition of proportionality in armed conflict, clarifying how international humanitarian law (IHL) relates to emerging domains such as cyber and autonomous weapons, and forging an additional set of tacit norms aimed at building a more substantive global culture of accountability and compliance with IHL.

While it is undeniable that the rules and principles of IHL have been violated since their inception, these violations themselves should not be considered as eroding the power of this legal regime. Rather, IHL is, at times, consecrated in the breach — it is strengthened and reaffirmed when atrocities are widely recognized as violations of the law. Nonetheless, today, the world is witnessing increasingly elastic interpretations of what is permissible under IHL beyond what is tolerable to humanity or militarily necessary.

By reaffirming their commitment to abide by the rules of warfare and further developing key IHL norms, states can underscore the importance of adhering to the principles of jus in bello, even in situations where resorting to war may be justified under jus ad bellum. Moreover, political measures taken alongside this process can also reduce the likelihood of such wars erupting and contribute to reducing their duration or severity.

High Contracting Parties should develop and codify universal and public standards for incidental harm assessment. These should take into account, among other things, the types of weapons (i.e., accuracy, yield, and secondary effects); the context in which such weapons are used; the location, concentration, and vulnerability of civilians and civilian objects present; and the short- and long-term public health and environmental consequences of a given attack.² Decisions should address how to apply these standards to state and non-state actors.³ This would increase protections for civilians, help to overcome existing double standards, and, therefore, avoid the fragmentation of the paradigm.

In addition to issuing statements endorsing their collective interpretation of the principle of proportionality in a way that places a high value on civilian life and objects, which have merit in themselves, states should take concrete steps in this direction. Such steps should include making explicit, for those states that have not done so already, the notion that a party must consider both direct and indirect effects on the civilian population. These indirect effects, particularly of attacks on infrastructure, frequently have severe, widespread, and lasting consequences for civilians and do not currently carry sufficient weight in proportionality assessments by various armed actors. Any harm, no matter how indirect, that is reasonably foreseeable must be considered, including, for example, downstream effects of disruptions to energy infrastructure, effects on the natural environment itself and as it relates to civilians, and the ability of humanitarian actors to deliver necessary assistance. Such considerations are particularly relevant when engaging in target analysis and selection before and in preparation for armed conflict, not merely during ongoing operations.

To that end, this report proposes the following courses of action:

1. Pursuant to Article 7 of Additional Protocol I to the Geneva Conventions, High Contracting Parties should agree to convene to explore how to strengthen adherence to the letter and the spirit of the conventions. This process should not be directionless but instead have the express intention of strengthening the protective nature of the conventions. Specifically, the mandate of this process should be for states to commit themselves to adopting strengthened interpretations of the fundamental principles of distinction, precaution, and proportionality that are rooted in the protective nature of IHL by way of a new, additional protocol.
2. As part of this process, states should also ensure that international law is up to the task of regulating twenty-first-century warfare, particularly relating to cyber operations and the use of autonomous weapons and artificial intelligence.
   • Whether by adopting national positions that interpret IHL more broadly or by developing new standalone legal standards, High Contracting Parties should clarify that IHL applies to cyber operations and that the protections afforded to civilian objects apply equally to digital civilian objects, such as computer networks and data. They should also clarify when and how a cyber operation can trigger an armed conflict and when it would amount to a use of force or armed attack under jus ad bellum to avoid a scenario in which state behavior that is misunderstood or misinterpreted by the other side erupts into war.
   • In line with the joint call by the U.N. Secretary-General and the president of the International Committee of the Red Cross, states should develop new legally binding rules on autonomous weapons systems (AWS). These rules should prohibit unpredictable AWS and anti-personnel AWS. In addition, there is a need to establish clear regulations for the use of all other types of AWS. For example, limiting the types of objects they can target to only those that are military by nature, limiting the circumstances in which AWS can operate, limiting the number of engagements or amount of time such systems can operate before requiring reauthorization by the human user, or ensuring the ability for a human user to supervise and, if necessary, deactivate operation.
   • The use of AI in military decision support systems (DSS) raises further concerns about the genuine level of human decision-making in the use of force. AI comes with all the biases of its developers, and it can develop new, unexpected ones. It can also be difficult to predict what an AI is going to do or understand why it did something. Additionally, humans are susceptible to falling into the “rubber stamp” trap, where we place too much trust and faith in the output of an automated process. AI DSS can also increase the pace of warfare to speeds that humans cannot meaningfully keep up with. Some AI tools may legitimately aid in the goals of complying with IHL and reducing humanitarian risks, but the issues that come with their adoption cannot be ignored. States and other relevant actors should set up a dedicated and inclusive forum for intensive and ongoing dialogue about (a) best practices for implementing IHL in relation to the use of AI, (b) whether existing IHL addresses all relevant concerns, and (c) how to fill any identified gaps, adapting, as needed, to new developments in the technology. Such a forum should be convened under the auspices of the U.N., taking as a possible structural inspiration the “Open-ended Working Group on the security of and in the use of information and communication technologies 2021-2025,” with all states as decision-makers and other actors — such as academia, civil society, and the private sector — as consultative stakeholders.⁴ This would contrast with existing fora, which often exclude key actors or are not structured as a standing forum focusing specifically on AI.
3. An additional goal should be for states to strengthen their collective interpretation of Common Article 1 to the four Geneva Conventions to “ensure respect” for their provisions through tangible actions. This stronger interpretation would center on an “external” obligation to seek compliance with IHL from all other states and parties (which is the way most, but not all, states interpret it) instead of only an “internal” obligation asserting that one must only ensure respect on the part of one’s own population. By developing common understandings on reducing the human costs of war and reducing the supply of arms to IHL violators, states could strengthen Common Article 1 without altering its text. Suggested measures include:
   • A joint declaration by all members of the G20 not to furnish military assistance to states engaged in wide-scale violations of IHL. This would be aimed at fostering common behavioral norms between established great powers and rising middle powers.
   • The establishment of — and political commitment to maintain — dedicated bilateral channels, especially between great powers, whose purpose is to deliberate whether the actions of one or the other interlocutor rise to the level of abetting or supplying states engaged in mass atrocities or aggression, the aim of which would be to replace coercive diplomacy with dialogue.
   • A public commitment among the United States, Russia, and China — which other rising powers would be free to join — not to instigate and enable indirect wars against one another. 

Proposal 5: Constraining interpretations of self-defense

The contested nature of sovereignty has led to a deterioration of the international order over recent decades. It will be necessary, therefore, to impose further constraints on the use of force on the territory of another sovereign state. Through a U.N. Security Council resolution, adopted under Chapter VII of the U.N. Charter, the international community should clarify that the Charter prohibits any state from invoking self-defense against a non-state actor operating in another state without the consent of either the second state or the Security Council unless the second state’s government is hosting the non-state actor in question as a matter of explicit policy.

Article 2(4) of the U.N. Charter prohibits the use of force against the territorial integrity or political independence of any state or in any other way inconsistent with the purposes of the United Nations. However, the Charter also recognizes the right of self-defense under Article 51 if an armed attack occurs. Article 51 confers the right to launch a necessary and proportionate response to an armed attack that has already occurred, and it is generally also considered to permit a state to prevent an imminent armed attack. The right to self-defense does not permit purely retaliatory, tit-for-tat strikes.

The contested nature of sovereignty has led to a deterioration of the international order over recent decades. It will be necessary, therefore, to impose further constraints on the use of force on the territory of another sovereign state.

States have taken different and, at times, permissive interpretations of what these two articles have to say about the lawfulness of responding with force to an armed attack launched by a non-state actor from the territory of a second state without that state’s approval. Clarifying this distinction through a new resolution would raise the bar for intervention.

The proposed resolution would reaffirm the centrality of the U.N. Charter and international law in regulating state conduct and the use of force. Given that many states already endorse this legal reading, the adoption of such a resolution is not unprecedented but rather a crucial step toward ensuring global stability. This resolution neither condones the harboring of terrorist organizations nor does it make it less dangerous for states to allow armed groups to operate in their territory. Rather, it limits the path to use force in these situations, requiring either Security Council authorization or consent from the second (host) state.

We assess that the adoption of this resolution would likely lead to the following shifts in state conduct:

• States would likely reassess their military doctrines and operational practices, shifting toward greater emphasis on intelligence gathering, surveillance, and reconnaissance to enhance situational awareness and early warning capabilities. 
• Though this measure would likely have a lesser impact on the conduct of great powers compared to middle powers, it would nevertheless raise the cost for great powers to engage in unauthorized military strikes, which could cause great powers to recalibrate their strategies and put greater emphasis on diplomacy, deterrence, and international cooperation.
• Harboring terrorist organizations, even if done short of explicit state policy, would carry greater risk in terms of international isolation and being subjected to multilateral military action under Chapter VII of the U.N. Charter. The international community should consider consequences for states that harbor violent non-state actors or arbitrarily deny consent for an aggrieved state to use force to counter such a threat. Such consequences could include, for example, multilateral sanctions or even the loss of some rights and privileges of U.N. membership for persistent failure to uphold international peace and security.

The adoption of this resolution reaffirms the legally binding obligation of the international community to prioritize and enforce sovereignty and the rule of law in addressing transnational security threats. It delineates the legal parameters surrounding preemptive military interventions and establishes a foundation for the enforcement of accountability against states found to be in breach of international law. And crucially, it aims to reduce the scope for interstate violence and reaffirm the importance of the norm of sovereignty in an increasingly unpredictable world.

This proposal attempts to reduce instances in which states use force as a first resort in response to an armed attack by a non-state group. It is complemented by this report’s proposals on U.N. Security Council reform, which, if implemented in the short term, would bring about a less gridlocked Security Council with new learned habits of behavior.

First, an expanded group of permanent members would be less likely to resort to the veto, given the increased political costs of casting an isolated negative vote in the face of opposition from seven other permanent members and 15 non-permanent members (at least five of whom are likely to be significant regional powers). Second, we have proposed measures that aim to reduce the ironclad nature of the veto, rendering isolated and frivolous vetoes subject to a potential General Assembly override.

This proposal carefully balances the legitimate right to self-defense with the principle of state sovereignty while leaving sufficient room for flexibility in state action and decision-making, including, for instance, the question of how precisely to determine whether a state hosts a group as a matter of explicit policy. That said, although adherence to this new norm risks being selective, a state attacked by a non-state actor will have greater reason to trust the Security Council to act and, by doing so, tie the application of self-defense more closely to the goal of preserving international peace and security.

1. Jus ad bellum concerns the body of law that pertains to justifying resorting to the use of force, whereas jus in bello refers to the law governing the conduct of wars that are already underway. ↩︎
2.  Such standards must not adversely distinguish on the basis of race, color, sex, language, religion or belief, political or other opinion, national or social origin, wealth, birth or other status, or any other similar criteria. See Geneva Convention Relative to the Protection of Civilian Persons in Time of War (Fourth Geneva Convention), August 12, 1949, 75 UNTS 287, arts. 3, 13; Protocol Additional to the Geneva Conventions of August 12, 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), June 08, 1977, 1125 UNTS 3, art. 75; Protocol Additional to the Geneva Conventions of August 12, 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), June 08, 1977, 1125 UNTS 609, art. 4. ↩︎
3. See Won Jang, “For whom the bell of proportionality tolls: Three proposals for strengthening proportionality compliance,” International Review of the Red Cross, Vol. 102, no. 914 (2020): 629-57. ↩︎
4. United Nations, “Open-Ended Working Group on Information and Communication Technologies,” UN Office for Disarmament Affairs, 2021, https://meetings.unoda.org/open-ended-working-group-on-information-and-communication-technologies-2021. ↩︎