Ukraine Symposium – War Termination: Legal Implications for International Security

The Kremlin announced on June 20 that it would finalize a date for a third round of peace talks with Ukraine. This follows two meetings in Istanbul on May 16 and June 2, 2025, marking the first such negotiations in over three years. But Ukraine and Russia remain worlds apart as Moscow presses sweeping demands, including formal recognition of its annexations. Russian President Putin recently declared “all of Ukraine is ours,” making clear that any settlement must legitimize Russia’s control. On July 5, President Trump indicated he was “very unhappy” with a July 3 phone call between the two leaders. “It just seems like [Putin] wants to go all the way and just keep killing people. It’s not good,” Trump told reporters. As peace talks reemerge and appear to stall again while drone attacks intensify, a critical question remains: can any future settlement uphold international law and deter future aggression, or will it reward unlawful conquest?

The war in Ukraine is a critical test of the international system’s ability to uphold legal norms underpinning global security. Article 2(4) of the UN Charter and its prohibition on acquiring territory by force is a cornerstone of post-World War II deterrence and directly supports U.S. interests in alliance credibility, global stability, and economic security. As a leading supporter of Ukraine, the United States will help shape any negotiated outcome. Yet when an aggressor like Russia occupies territory without being overthrown or unconditionally defeated, war termination raises legal and strategic dilemmas. The tension between jus ad bellum (the laws governing resort to war) and jus post bellum (the laws governing post-war settlements) becomes acute. At the center lies a fundamental question: Can this war reach a negotiated settlement without undermining the prohibition on territorial conquest, and if so, how?

This post analyzes legally permissible options for ending the war in Ukraine and argues that U.S. strategy must account for their varying implications for international security. The central thesis is that preserving the prohibition on territorial conquest in Article 2(4) through non-recognition, rejection of coerced settlements, and legal attribution of responsibility for Russia’s territorial aggression is essential not only to Ukraine’s sovereignty but also to the credibility of deterrence as a function of U.S. grand strategy. In support of this thesis, the post makes three interrelated claims.

First, international legal norms are strategic assets and foundational to deterring aggression, particularly in an era of systemic competition and hybrid warfare. When consistently upheld, these norms reinforce the credibility of U.S. security commitments and constrain the behavior of revisionist States. Second, this post contends that not all legally permissible pathways to ending the Ukraine War are equal in their strategic implications. Some options, such as ceasefires that freeze territorial gains or peace agreements that reward aggressor States, may be lawful, but they carry risks to international security and erode deterrence (see here). Third, sacrificing legal principles for the sake of short-term diplomatic flexibility risks legitimizing aggression and weakening the very norms that make future wars less likely. A coherent U.S. strategy must therefore integrate legal enforcement into its deterrence posture, ensuring that the outcome of this war does not incentivize future violations of international law.

Russia: The Principal Violator of Article 2(4)

Since the adoption of Article 2(4), territorial conquest in Europe has been rare. Broad legal and diplomatic rejection of coercive border changes helped contain such acts during the Cold War and its aftermath. This restraint was reinforced by the 1970 UN General Assembly Resolution 2625, which clarified that “no territorial acquisition resulting from the threat or use of force shall be recognized as legal.” However, in recent decades, that restraint has weakened. Russia has become the principal violator of Article 2(4), engaging in sustained and often permanent seizures of territory. Since 2008, it has gained or maintained control of Crimea, Luhansk, and parts of Donetsk in Ukraine, South Ossetia and Abkhazia in Georgia, and Transnistria in Moldova. These areas are not recognized as independent countries under international law, though some claim to be States or are de facto controlled by separatist or occupying powers. Russia’s actions are not isolated but part of a strategic approach that normalizes aggression through proxies, referenda, and annexation (see here and here). If unchallenged, this approach threatens to erode Article 2(4)’s deterrent value and embolden future violations.

Russia’s interventions in Moldova, Georgia, and Ukraine follow a consistent trend: seizure, prolonged occupation, and political integration, sometimes formalized by annexation and producing sustained territorial losses and de facto border changes. Ukraine’s sovereignty was clearly established in 1991, with over 90 percent of voters, including a majority in Crimea, supporting independence. Russia recognized this through the Minsk and Alma-Ata Agreements, reinforced by the 1994 Budapest Memorandum, in which Russia pledged to respect Ukraine’s borders in exchange for nuclear disarmament. The 1997 Treaty of Friendship further codified these commitments.

A coherent U.S. strategy must treat legal principles not only as constraints but also as strategic assets. The war in Ukraine presents a critical test: whether the United States and its allies will continue to enforce the foundational norm that force cannot alter territorial borders. If this norm is diluted through coerced peace, acceptance of annexation, or recognition of illegally annexed territories, a central pillar of deterrence is at risk, with implications extending beyond Europe to the South China Sea and the Korean Peninsula. War termination is not merely a legal or diplomatic task but a strategic choice. The United States must balance the desire to end conflict with the imperative to preserve the legal architecture that helps prevent future wars. Deterrence depends not only on capabilities and alliances but also on legal clarity and normative consistency. This is particularly urgent when authoritarian States exploit legal ambiguity and gray zone tactics to challenge the existing international rules-based order. This post builds on this premise by analyzing legally permissible paths to war termination, evaluating them not only on their feasibility but on their contribution to strategic deterrence and international security.

Why Article 2(4) Matters: Grand Strategy and the Legal Foundations of Deterrence

U.S. national security and defense strategies consistently prioritize the rules-based international order. Central to this order is the prohibition on using force to acquire territory, codified in Article 2(4). This principle is not merely a legal restraint but a strategic commitment that affirms the illegitimacy of conquest and functions as a normative red line to deter aggression. This is especially consequential in Ukraine, where the integrity of Article 2(4) is under direct assault. Russia’s invasion and attempted annexation of Ukrainian territory violate international law and challenge the post-World War II security framework for Europe.

If these violations are met with ambiguity or de facto acceptance, they signal to Russia and other potential aggressors that aggressive war remains a viable path for political gain. Deterrence must be understood not only in operational but also in legal and normative terms. A grand strategy that neglects these foundations risks overlooking critical tools of conflict prevention.

Legal Pathways to Peace and Their Implications for International Security

Some options for ending the war in Ukraine carry greater risks to deterrence and international security than others. International law and jus post bellum offer three distinct legal instruments for conflict resolution: ceasefire, armistice, and a peace treaty. A ceasefire temporarily suspends hostilities but does not legally end the conflict. The risk is it can freeze gains of the aggressor without legal finality, as seen in the 1994 ceasefire in the Nagorno-Karabakh conflict, which failed to resolve core disputes and led to renewed violence. An armistice is more durable and legally ends the conflict, though it may not resolve underlying legal or political disputes. The 1953 Korean Armistice Agreement illustrates this model, ending combat without a final political settlement. A peace treaty offers the most comprehensive resolution and must conform to international legal norms, including respect for territorial integrity. The 1995 Dayton Accords ended the Bosnian War and functioned as a peace treaty in a contested sovereignty context, though such agreements are rare due to political complexity.

Beyond these three outcomes, international law recognizes several mechanisms that can influence conflict resolution. These include unilateral declarations, such as the Taiwan Relations Act of 1979 or political moves, such as Croatia’s 1991 declaration of independence, actions that, despite initial escalation, led to mediated resolution or peaceful reintegration. The UN Security Council has endorsed political agreements aimed at de-escalation, such as the Minsk Agreements through UNSCR 2202, but these efforts lacked effective enforcement. These mechanisms differ from peace treaties and are better understood as unilateral declarations or political actions with normative influence.

Territorial gains through war are illegal, even if later codified in a treaty. Only non-coerced concessions, unrelated to armed conflict, can be lawful. As affirmed by the Vienna Convention on the Law of Treaties, agreements procured through the threat or use of force are invalid (art. 52). Only voluntary concessions made absent coercion and unrelated to the use of armed force can have legal effect. Peace cannot validate illegality. This principle has deep roots, reflected as early as 1923 in the Permanent Court of International Justice’s Wimbledon decision, which underscored that the legality of State action cannot be determined solely by political outcomes but must rest on enduring legal norms. The 1974 UNGA Resolution 3314 Definition of Aggression further codifies this understanding. Article 5(3) declares that no territorial acquisition or special advantage resulting from aggression is or shall be recognized as lawful. Non-recognition, then, is essential to preserving the legitimacy of international law.

War termination must balance urgency with legal integrity. Ceasefires and armistices may stop violence but must not imply acceptance of unlawful territorial control. Peace treaties, where pursued, should be negotiated without coercion, without legitimizing territorial compromise, and in full conformity with international norms. The Erdut Agreement is one model, supporting phased reintegration of Eastern Slavonia into Croatia in 1995 under international supervision. Interim mechanisms must reinforce, not compromise, territorial integrity. Allowing aggressors to retain territory in violation of Article 2(4) weakens the legal prohibition on the use of force, erodes deterrence, and undermines the credibility of international law as a global strategic asset.

From this assessment, four mutually reinforcing strategies emerge to guide U.S. and international efforts. For U.S. national security leaders, they offer a legally grounded path for terminating the Ukraine war. These strategies fall into two categories: preventative strategies, which preserve long-term deterrence; and restorative strategies for international security, which manage ongoing conflict without compromising legal principles. This typology illustrates how law serves not only as a constraint on warfare, but as a proactive instrument for shaping peace.

The first three strategies are preventive in character and form the foundation of a legalist approach to deterrence. Their implementation requires a combination of unilateral commitments and multilateral coordination. They should be embedded in U.S. policy, elevated in national-strategic level messaging, and advanced through diplomatic engagement. The final strategy is restorative and can help manage ongoing conflict, reinforce legal standards, and help restore breaches in the international legal order.

Preventative Strategies: Shaping Future Behavior through Normative Clarity

Strategy 1: Reaffirm Non-Recognition of Territorial Gains by Force

Non-recognition of territory acquired through aggression is not merely a legal principle but the linchpin of international deterrence. It reinforces the norm that illegal acts cannot produce legal results (ex injuria jus non oritur), sending a clear message to revisionist powers that expansion through force will not be legitimized. In Europe, this strengthens the post-Cold War settlement and deters further Russian incursions. In Asia, it signals resolve as China tests boundaries in Taiwan and the South China Sea. The primary drawback is diplomatic rigidity: peace negotiations may stall if Russia refuses to enter talks that preclude recognition of its gains. These diplomatic obstacles must be weighed against the cost of weakening a foundational norm.

States can reaffirm non-recognition in UNGA resolutions and can also condition diplomatic and economic engagement on compliance. The legal principles referenced above encourage States to withhold recognition and avoid supporting illegal occupation of territory.

Strategy 2: Reject Coercive Peace Deals Involving Territorial Concessions

Legal principles must guide peace settlements. Even if Ukraine is pressured into a treaty recognizing Russian claims, such agreements are invalid under international law (as explained above). Peace treaties that legitimize territorial gains won by force set a dangerous precedent. This strategy affirms that treaties agreed under duress lack legitimacy and enhances international security by ensuring that peace agreements reflect legality, not capitulation. It affirms the distinction between ceasefires and armistices, which are temporary, and treaties that codify and implement permanent changes.

The United States and its allies should avoid frameworks that require Ukraine to cede sovereignty by coercion. Public and legal support for Ukraine’s territorial sovereignty reinforces its position and provides assurance to States like Moldova and Georgia facing similar threats. In Asia, it signals to China that military coercion will not result in recognition or favorable agreements. Critics argue this approach is inflexible, yet history shows legal compromise seeds future instability. Rejecting coercive deals maintains the integrity of peace.

Strategy 3: Strengthen Legal Attribution and Documentation Mechanisms

Russia’s use of proxies and lawfare, such as referenda and liberation rhetoric, to obscure responsibility and avoid accountability undermines the international order (see here). These tactics are central to Russia’s broader strategy of conquest. Attribution mechanisms, which identify perpetrators and document violations, are essential in responding to hybrid conflict and ensuring accountability. Addressing proxy warfare within a legal and strategic framework is essential to prevent aggressors from exploiting political ambiguity to undermine territorial integrity (for legal analysis regarding Russia’s use of the Wagner Group, for example, see here).

Russia’s use of proxies in Donetsk, Luhansk, Transnistria, Abkhazia, and South Ossetia delays international responses and creates legal ambiguity. Subversive annexation refers to covert or indirect State control over territory that lacks legal legitimacy. Russia’s use of proxy governments is not only intended to evade Article 2(4)’s prohibition on the use of force, but also to obscure legal responsibility for the events occurring in those territories.

International law must evolve to directly address occupations via proxy. The principle of non-recognition should extend to proxy-occupied zones, even where formal annexation has not occurred, reinforcing the idea that unlawful control by indirect means cannot yield lawful status. At the same time, structured peace frameworks must explicitly exclude proxies from negotiation or governance roles. Including entities installed or maintained through unlawful force risks legitimizing aggression and undermining the rules-based order. Any viable settlement must reflect the sovereign rights of the affected State, not the strategic interests of the aggressor’s intermediaries.

Restorative Frameworks: Managing the Present with Legal Integrity

Strategy 4: Shape Future Peace Frameworks Aligned with Legal Principles

Temporary frameworks can help manage conflict without formalizing illegal territorial changes. Historical models such as the Helsinki Accords, Baltic Non-Recognition (the longstanding U.S. and allied policy of refusing to recognize the Soviet Union’s forcible annexation of Estonia, Latvia, and Lithuania during and after World War II), and the Erdut Agreement demonstrate how temporary arrangements can create space for reintegration or future negotiation without legal recognition of territorial changes. In Europe, multilateral institutions can help monitor compliance. In frozen conflicts or ceasefire zones, stabilization agreements can prevent the re-escalation of violence while preserving future options for legitimate resolution. In the Indo-Pacific, where legal ambiguity is a strategic weapon, such frameworks may be misinterpreted as de facto recognition. Designed carefully, stabilization frameworks provide a mechanism to hold the line diplomatically while enabling phased reintegration or autonomy without conceding sovereignty.

Ceasefires and armistices are crucial humanitarian tools that can pause conflict without conceding legal rights. But their strategic value depends entirely on how they are framed and enforced. Both are legally neutral with respect to sovereignty and, if framed well, can serve as tactical de-escalation measures. Used correctly, ceasefires can be the first phase of a broader strategy that leads to stabilization and reintegration. Used poorly, they can entrench illegality. In Ukraine, any ceasefire proposal must rest on genuine commitment and be reinforced by unwavering non-recognition of Russia’s territorial claims.

Eroding Deterrence: The Danger of Abandoning Legal Commitments

As pressure builds to find a resolution for Ukraine, some may argue that rigid adherence to legal principles risks impeding diplomatic progress. From this perspective, strategic flexibility, including arrangements such as partial recognition, phased autonomy, or special administrative status offer a pragmatic path to peace, especially when the enforcement of legal norms is weak or when the humanitarian concerns demand urgent resolution. A few historical cases illustrate that strategic flexibility has, at times, helped resolve or deescalate intractable conflicts. For example, Sudan’s 2005 Comprehensive Peace Agreement granted the disputed region of Abyei a special administrative status, postponing final legal determination to preserve stability.

Yet the dangers of abandoning legal commitments in favor of expediency are profound. History shows that compromising legal norms invites future aggression. Russia’s aggression in Ukraine and elsewhere underscores the risks of tolerating unlawful territorial gains; it has resulted in sustained occupation, annexation attempts, and de facto border changes. Ukraine’s sovereignty was not ambiguous: it was clearly affirmed by Russia and reinforced through multiple legal instruments. These legal foundations were not abstract but explicit mutual commitments to uphold borders and reject aggression.

While the UNGA has passed several resolutions affirming Ukraine’s sovereignty, voting patterns reflect a fractured international response. Many countries in the Global South have abstained or expressed ambivalence, reflecting broader concerns about the politicization and selective enforcement of international law. Europe, including Central and Eastern Europe, was initially strongly supportive of Ukraine, but support has shifted as some countries prioritize energy security or neutrality. Despite robust financial and military assistance from the United States and European Union, the failure of broader multilateral and international coalitions to fully enforce Article 2(4) demonstrates how selective application of this norm undermines its deterrent value. Exceptions become precedents and the rules lose their constraining power. Legal ambiguity does not prevent war; it delays and complicates peace. Moreover, alliances built on shared legal principles suffer when those principles are inconsistently upheld. Small States relying on international law for security lose faith, while great powers emboldened by impunity escalate demands. Strategic deterrence depends on consistency, credibility, and clarity.

In response to these challenges, efforts to reinforce legal norms through concrete, principle-based actions are essential for restoring credibility and shaping durable outcomes. The recent U.S.-Ukraine minerals deal offers a step towards shaping a just and sustainable peace framework by affirming principles of Ukraine’s sovereign ownership over natural resources and linking war termination aims to economic reconstruction. While not a comprehensive solution, it reflects the logic of all four strategies by reinforcing non-recognition of territorial conquest, rejecting coercive bargaining, challenging conflict through investment and signaling economic recovery, incentivizing lawful behavior over the use of force, and beginning to lay the institutional and political groundwork for a durable future negotiated settlement.

The international response to Russia’s aggression through UNGA resolutions, non-recognition policies, legal condemnation, and forward-leaning agreements between allies and partners, have helped reaffirm Article 2(4)’s prohibition on the use of force. But these commitments must continue to guide the terms of peace. Agreements that compromise Ukraine’s territorial integrity or embed illegal gains into negotiated outcomes will not achieve lasting peace. Instead, they will erode the very legal architecture that has prevented great power war for decades.

Conclusion: The Legalist Path as a Foundation for International Security

The war in Ukraine is not just about sovereignty. It is a test of whether international law can withstand 21st-century aggression. Meaningful war termination must uphold the legal norms that deter future wars. National security strategy should integrate a legalist approach: reaffirm non-recognition, reject coercive peace deals, strengthen legal attribution for aggression, support legal stabilization frameworks, and counter proxy warfare. These are not isolated strategies but part of a broader approach that reflects a strategic commitment to upholding international law as a foundation for lasting international security. International law must adapt to new threats while preserving its core principles. If it does, it can remain what it was always intended to be: the world’s best defense against the return of force as the ultimate arbiter of international affairs.

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CDR Andrea M. Logan is a U.S. Navy judge advocate and a recent graduate of the Naval War College.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense. 

Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.

Photo credit: Mstyslav Chernov