Since late December 2025, protests across Iran have been met with a State response that can only be described as extraordinary in scale and brutality. Amnesty International has called January 2026 the deadliest period of repression it has documented in Iran in decades, citing mass killings alongside widespread arbitrary detentions and enforced disappearances. Taken together, the Iranian regime’s response to recent protests almost certainly amounts to the commission of crimes against humanity.
At the same time, the broader geopolitical context has shifted dramatically. Against the backdrop of these widespread and systematic human rights violations, U.S. President Donald Trump has significantly bolstered the U.S. military posture toward Iran. The White House is planning for what U.S. officials describe as a possible weeks-long military campaign should negotiations over Iran’s nuclear program falter. U.S. Navy assets, including the USS Abraham Lincoln and the USS Gerald R. Ford (the world’s largest warship), have been deployed to the Gulf, alongside additional destroyers, carrier strike group escorts, and air force elements, in a build-up that U.S. officials acknowledge is intended to strengthen Washington’s leverage in diplomatic talks. Altogether, this amounts to the largest gathering of U.S. military assets in the Middle East since the Second Gulf War. In Israel, Prime Minister Benjamin Netanyahu has also ordered the Israeli Home Front Command to prepare for a potential war with Iran.
Together, these dual crises are challenging international law and the institutions meant to uphold it. Accountability for the widespread abuses in Iran remains sorely lacking, but the use of military force is an imperfect and legally constrained tool for achieving it. Any potential U.S. strike against Iran’s nuclear program would confront substantial international and domestic legal limits, particularly absent an imminent threat of armed attack on the part of Iran, and risks weakening rather than strengthening the legal order such action might seek to defend. Below I examine the accountability pathways that international law does provide, from United Nations fact-finding mechanisms to universal jurisdiction cases and international courts, not as comprehensive solutions, but as the limited and often delayed tools available within the existing legal framework. Iran thus emerges as a central test of whether the rules-based order can respond lawfully and coherently to mass repression even when its mechanisms struggle to deliver timely protection.
The Islamic Republic’s Violent Crackdown
Although casualty figures remain contested amid severe information restrictions, the Islamic Republic has acknowledged more than 3,000 deaths since Dec. 28 when demonstration began. The U.S.-based Human Rights Activists News Agency (HRANA) reports over 7,000 verified deaths and thousands more under investigation, suggesting totals likely exceed 20,000. Mai Sato, U.N. Special Rapporteur on the situation of human rights in the Islamic Republic of Iran, has cited a more conservative estimate of around 5,000 deaths, while noting that medical sources have reported unverified figures reaching up to 20,000. Even the lower-end estimates would make this crackdown among the deadliest episodes of state violence against protesters in contemporary Iranian history, while higher-end figures would place it among the most lethal episodes of protest repression globally in recent decades.
Compounding the violence are credible reports that authorities have further traumatized victims’ families while attempting to obscure the scale of the killings. Testimony from medics, morgue workers, and cemetery staff further points to a concerted state effort to conceal the scale of killings, while Sato told Reuters that families have in some cases been forced to pay authorities between $5,000 and $7,000 to retrieve the bodies of loved ones, an especially crushing burden amid Iran’s deepening economic crisis. Recent footage also shows security officials shooting at mourning family members during commemoration ceremonies that occur 40 days after someone’s death.
On their face, these acts constitute clear violations of Iran’s obligations under international human rights law and almost certainly amount to crimes against humanity, echoing conclusions reached by the U.N. Fact-Finding Mission on Iran in March 2024 concerning the violence following the killing of Mahsa Amini and the subsequent Women, Life, Freedom protests. The large-scale use of lethal force against largely unarmed demonstrators, mass detentions, torture and ill-treatment, internet shutdowns, and fundamentally unfair trials point to systematic repression rather than isolated excesses. Concentrated mass killings over a short period, coupled with coordinated efforts to suppress evidence, fit many of the indicia prosecutors and commissions of inquiry treat as hallmarks of a “widespread or systematic” attack on a “civilian population,” which separates crimes against humanity from other human rights violations.
International and Domestic Legal Constraints on a U.S. Military Attack on Iran
In the shadow of ongoing U.S. threats of military action, indirect negotiations have resumed in an effort to de-escalate tensions. Talks in Oman and, most recently, in Geneva have focused on Iran’s nuclear program and military capabilities, without any apparent engagement on the country’s ongoing human rights crisis. Meanwhile, officials in Washington, including Vice President JD Vance, acknowledge that the two sides remain far apart on core issues, and credible reporting indicates that the U.S. military is actively preparing for the possibility of a significant, potentially weeks-long operation against Iran if talks collapse — underscoring that the threat of force is being used as leverage in nuclear negotiations rather than as a mechanism tied to accountability for human rights abuses.
International law: Article 2(4), Article 51, and the legality of threatened force
Under the U.N. Charter, the default rule is clear: States must refrain from the threat or use of force against the territorial integrity or political independence of any State (Article 2(4)). Thus, the two lawful bases for the use of force against another State are:
- U.N. Security Council (UNSC) authorization under Chapter VII; or
- Self-defense under Article 51, in response to an armed attack (or, under many States’ views, an imminent one), subject to necessity and proportionality.
The Responsibility to Protect (R2P) principle — discussed more below — standing alone, does not supply a third legal pathway.
Accordingly, when the United States threatened force against Iran in response to its recent brutal crackdown, it would have needed to anchor its justification in self-defense (potentially including collective self-defense). On the facts publicly available, however, it is difficult to identify a self-defense justification that would satisfy the requirements of Article 51. Similar legal challenges arise with respect to potential military action tied to Iran’s nuclear program.
Recent U.S. military deployments and statements reportedly intended to reinforce negotiating leverage also underscore a related legal constraint: international law treats the threat of an unlawful use of force as itself unlawful, as emphasized by the International Court of Justice in its advisory opinion on the Legality of the Threat or Use of Nuclear Weapons. Where military deployments and public statements are designed to coerce concessions, and in the absence of an armed attack or imminent threat thereof, they can trigger the prohibition on the unlawful threat of force also codified in Article 2(4).
These bedrock rules of the international system present several recurring legal problems for a use of U.S. military force against Iran in the present context.
First, public reporting to date does not identify an armed attack by Iran against the United States, or imminent threat thereof, that would clearly satisfy the Article 51 threshold. Although some U.S. officials reference broader regional threats or nuclear advances, the legality of preemptive self-defense remains contested at best. Claims untethered from a specific, imminent armed attack — particularly where force is framed as leverage in nuclear negotiations — sit uneasily within even expansive readings of Article 51. If the objective is to prevent future nuclear capability or compel changes in ballistic missile posture, rather than to repel or halt an ongoing or imminent armed attack, the legal theory begins to resemble preventive or coercive force, categories that the Charter was designed to prohibit.
Second, a sustained campaign designed to degrade capabilities or extract strategic concessions would be difficult to square with any accepted version of self-defense. Self-defense does not permit force to punish, deter in general, or coerce policy change. Nor does it authorize regime change. The broader and more strategic the objective becomes, the more strained any self-defense rationale would appear. Reporting that U.S. military planners are preparing for a potentially weeks-long campaign targeting nuclear and broader security infrastructure heightens this concern.
Finally, linking potential strikes to Iran’s ongoing human rights atrocities introduces a separate complication. Many observers argue, with understandable moral force, that mass repression rising to the level of crimes against humanity should permit or even require outside intervention when peaceful measures fail. Yet under prevailing interpretations of international law, unilateral humanitarian intervention absent Security Council authorization remains legally controversial and is rejected by most States as inconsistent with the Charter.
At present, moreover, negotiations in Oman and Geneva reportedly focus narrowly on nuclear and related security issues, with no apparent inclusion of Iran’s human rights crisis. This omission further weakens any attempt to frame military threats as grounded in atrocity prevention rather than nuclear leverage. In practice, the more prominently human rights justifications are invoked, the more difficult it becomes to situate the use of force within established self-defense doctrine. Likewise, the more explicitly force is tied to nuclear bargaining, the more it risks being characterized as unlawful coercion under Article 2(4). The current dual-track posture, active diplomacy combined with operational planning for a sustained campaign, therefore reflects an unresolved tension within the legal framework rather than a clear pathway through it.
U.S. domestic law: Article II, Congress’ war powers, and the War Powers Resolution
In the United States, any use of military force, especially outside a narrowly confined self-defense context, must grapple with the constitutional allocation of war powers and the statutory constraints of the War Powers Resolution (WPR).
Article I of the U.S. Constitution grants Congress the power to declare war, to raise and support armies, and to make rules governing the armed forces, alongside numerous other war-related powers. Article II designates the president as commander-in chief, traditionally understood to permit the president to “repel sudden attacks” based on the authority provided in this clause – that is, to engage in only limited defensive actions without prior congressional authorization. The contours of these constitutional authorities have long been contested, with the executive branch over recent decades arrogating more power to itself at the expense of Congress.
A recent flashpoint in this ongoing contest was, of course, the January 2026 U.S. military operations in Venezuela that resulted in the capture of Nicolás Maduro, and his wife. As articulated in this Just Security piece, the operation did not rest on statutory authorization and relied instead on expansive and contested theories of inherent Article II power. Far from reflecting settled precedent, the episode exposed the fragility of such presidential claims to unilateral authority to use force and triggered congressional debate under the War Powers Resolution.
In any event, it would be difficult to analogize even the unprecedented Venezuela operation to a potential weeks-long campaign against the Islamic Republic. It should be beyond dispute that a sustained military campaign targeting Iranian nuclear facilities, missile infrastructure, or broader security assets would trigger an international armed conflict between the United States and Iran, a war “in the constitutional sense,” as the Department of Justice’s Office of Legal Counsel (OLC) has described those uses of military force that require congressional authorization under Article I of the Constitution. The scale, duration, escalation risks, likelihood of harm to U.S. interests, and strategic ambition of such an operation would move well beyond the “limited defensive” category that presidents have often invoked to justify unilateral action under Article II.
Moreover, a campaign designed to degrade capabilities or coerce strategic concessions, particularly in the context of nuclear negotiations, would be difficult to characterize as repelling a sudden attack or protecting U.S. forces from immediate harm. That distinction matters constitutionally. The further an operation departs from immediate defense and approaches sustained hostilities against another State, the stronger the Article I argument becomes that Congress must authorize the action.
Put differently, whatever elasticity presidents have claimed in recent years, a weeks-long campaign against Iran would test – and arguably break – the outer boundary of unilateral executive authority. It would implicate the very core of Congress’ war powers, making explicit authorization not merely prudent as a political matter, but constitutionally required under the separation-of-powers framework.
As others have explained at length, the War Powers Resolution (WPR) was enacted to reinforce that constitutional balance. It requires the president to notify Congress within 48 hours of introducing U.S. armed forces into hostilities or situations where hostilities are clearly indicated, and it generally limits the duration of such hostilities to 60 days, with the potential for a further 30-day withdrawal period, absent a declaration of war or an explicit congressional authorization for the use of military force (AUMF). It also provides mechanisms for Congress to terminate uses of U.S. armed forces abroad, though those have been severely weakened in recent decades.
Congress’ series of debates over proposed Iran war powers resolutions reflect this concern; lawmakers have introduced measures to require explicit congressional approval before U.S. forces engage in unauthorized hostilities related to Iran, emphasizing that sustained use of force should not occur without deliberative legislative assent.
Finally, it merits noting that there is “no existing congressional authorization for the use of force against Iran.” While during President Trump’s first term the notion was floated that the 2001 AUMF could plausibly be stretched to cover a strike on Iran, there is no serious argument that this is a viable interpretation of that statute, which was of course enacted to permit the use of force against those who planned and carried out the 9/11 attacks, and has nothing to do with Iran or its nuclear program.
The Responsibility to Protect: What R2P Does, and Does Not, Authorize
Even putting aside that President Trump’s stated objective is to remove Iran as a nuclear or significant military threat in the region, what of the human rights of the Iranian people who continue to suffer under a dictatorial and authoritarian regime? To that end, the ongoing human rights crisis has revived calls to invoke the international Responsibility to Protect (R2P) framework.
The R2P framework was unanimously adopted in 2005 at the U.N. World Summit, the largest gathering of Heads of State and government in history. It is articulated in paragraphs 138 and 139 of the World Summit Outcome Document and best understood as a framework with three “pillars”:
- States have a primary responsibility to protect their populations from genocide, war crimes, ethnic cleansing, and crimes against humanity.
- International assistance and capacity-building are needed to help States meet that responsibility.
- Timely and decisive collective action, through the U.N., and in accordance with the U.N. Charter, may be needed when a State is “manifestly failing” to protect its population.
Organizations that monitor atrocity risk, including the Global Centre for the Responsibility to Protect, have warned that Iranian authorities may be committing possible crimes against humanity through mass killings and arbitrary arrests, placing populations at imminent risk. This language maps onto R2P’s core trigger concerns. And, for the reasons noted above, the ongoing violence against protestors and their family members by the Islamic Republic appears to prima facie meet the test for crimes against humanity.
But R2P is often misunderstood in precisely the way that matters most in the present moment: R2P does not create a freestanding legal entitlement for unilateral military intervention (despite a small handful of States, notably not including the United States, having at times built on this framework to embrace “humanitarian intervention” as a basis for the unilateral use of force that would otherwise be unlawful). Rather, its “collective action” pillar is anchored in U.N. Charter mechanisms, especially action authorized by the U.N. Security Council under Chapter VII. In practice, that means R2P’s strongest immediate legal and policy implications typically concern:
- Fact-finding and monitoring (including U.N.-mandated investigations),
- Targeted sanctions and travel bans,
- Arms restrictions,
- Evidence preservation and documentation support,
- Diplomatic isolation and accountability signaling, and
- Humanitarian measures and protection of refugees.
Recent steps by States and international bodies, ranging from additional sanctions by the European Union on Iranian officials and entities to intensified multilateral scrutiny, fit within this “non-forcible” R2P toolset. This also includes the resolution by the U.N. Human Rights Council on Jan. 23 to extend the mandate of the Independent International Fact-Finding Mission on Iran for two years, and the mandate of the Special Rapporteur on the situation of human rights in Iran for one year, and expressly calling for an urgent investigation by the Fact-Finding Mission into the existing protest violence since Dec. 28, 2025.
The harder question, whether the Security Council would authorize coercive measures, including force, runs into the familiar problem of geopolitics and veto power. That reality does not make R2P irrelevant; it shifts the emphasis to mechanisms that can be deployed without Security Council unity, while preserving the Charter’s baseline prohibition on force.
Accountability Options: From U.N. Mechanisms to Universal Jurisdiction
If the violence in Iran amounts to crimes against humanity (or other atrocity crimes), what can be done, particularly since ongoing negotiations and any U.S. military attack is unlikely to focus on the human rights issue? The answer is not a single forum but an ecosystem of accountability mechanisms, some legal, some political, many complementary. These tools may preserve the possibility of justice over time, but, as discussed below, they offer little prospect of stopping the violence as it unfolds.
1) U.N. fact-finding and evidence architecture
In the near term, U.N. investigative processes remain among the most viable accountability tools where domestic avenues are blocked and international criminal jurisdiction is uncertain. As mentioned, the U.N. Human Rights Council has already decisively extended the mandate of the Independent International Fact-Finding Mission on Iran for an additional two years and the mandate of the Special Rapporteur on the situation of human rights in Iran for one year, explicitly calling on the mission to conduct an urgent investigation into the serious human rights violations and crimes perpetrated in the context of the nationwide protests that began on Dec. 28.
These extensions reflect a Human Rights Council judgment that domestic mechanisms remain unable or unwilling to credibly investigate or remedy the abuses, and that continued international monitoring and evidence-gathering are necessary. The mission’s mandate, to establish facts, document human rights violations, and preserve evidence for potential future legal proceedings, is especially important given the Iranian government’s internet shutdowns and information suppression, which have made independent verification of events extremely difficult.
U.N. fact-finding mechanisms do not themselves prosecute, but they can create authoritative records that could empower later accountability efforts. Experience from Syria, Myanmar, and other contexts shows that documentation generated under U.N. auspices often becomes the evidentiary backbone for prosecutions in domestic courts exercising universal jurisdiction or for use in other tribunals. Moreover, the very act of international investigation can strengthen the political and legal case for sanctions, travel bans, and other measures that impose cost on perpetrators and help protect victims.
2) The International Criminal Court: Possible, but procedurally difficult
The International Criminal Court (ICC) remains the most visible forum for atrocity prosecutions, but Iran presents formidable jurisdictional barriers. The country is not a party to the Rome Statute, meaning the Court lacks ordinary territorial or nationality jurisdiction unless Iran accepts jurisdiction or the U.N. Security Council refers the situation, an outcome that current geopolitical realities make unlikely.
Some advocates have attempted to extend the Court’s jurisdiction through the precedent set in the ICC’s decision concerning the Myanmar/Bangladesh situation. In that case, the Court held that it could exercise jurisdiction over deportation as a crime against humanity because part of the criminal conduct, the crossing of an international border, occurred on the territory of Bangladesh, a State Party to the Rome Statute. By analogy, some argue that if individuals fleeing persecution in Iran are forcibly deported into countries that are ICC member States, the Court might assert jurisdiction over at least portions of the crime.
There are, however, reasons for caution. The Myanmar/Bangladesh decision itself was controversial, seen by many observers as a politically driven effort by ICC judges to expand the Court’s reach beyond its earlier concentration on African crimes. Several of the Court’s most significant financial and diplomatic backers privately view the ruling as jurisdictional overreach, worrying that creative interpretations risked undermining the Court’s legitimacy and cooperation prospects. Applying that reasoning to the Islamic Republic would stretch jurisdiction even further, particularly given the complexity of distinguishing voluntary flight from deportation and establishing that deportations were integral to a state policy constituting crimes against humanity.
Put bluntly, while creative jurisdictional theories exist, the practical likelihood of ICC jurisdiction over Iran in the absence of a Security Council referral remains limited and efforts to force the issue risk further politicizing an already fragile institution, an issue Court principals are themselves deeply attuned to in light of existing pressures posed by U.S. sanctions.
3) Universal jurisdiction in domestic courts
Domestic courts exercising universal jurisdiction present a more immediate and realistic avenue for accountability, particularly where suspects travel abroad or where diaspora communities can initiate proceedings. Under universal jurisdiction statutes, several States permit prosecution of genocide, crimes against humanity, and war crimes regardless of where they were committed, provided certain jurisdictional conditions are met.
Recent experience demonstrates both the promise and the limits of this pathway in the Iranian context. In Sweden, prosecutors successfully pursued proceedings against an Iranian official involved in the mass executions of political prisoners in 1988, culminating in a landmark conviction under universal jurisdiction principles. The case illustrated how diaspora testimony and documentation collected over decades can eventually support criminal accountability once suspects travel into jurisdictions willing to act. Though notably, that individual was later released to Iranian authorities as part of a prisoner swap.
Similarly, courts in Argentina are entertaining proceedings invoking universal jurisdiction in relation to grave international crimes allegedly committed by Iranian officials, demonstrating that accountability efforts may arise even far from the territorial locus of abuses when domestic courts accept jurisdiction over international crimes.
These cases nonetheless reveal practical constraints. Proceedings typically depend on suspects entering prosecuting jurisdictions, require sustained political and prosecutorial commitment, and often take years to develop. Sitting senior officials may also benefit from personal immunities while in office, limiting immediate reach. Yet such cases serve important purposes: they establish judicial records, narrow safe havens for perpetrators, and signal that time and distance do not necessarily foreclose accountability.
A Stress Test for the Rules-Based Order
Across all accountability pathways, the immediate priority is not jurisdictional innovation but evidence preservation. Where authorities suppress information, intimidate families, and restrict communications, documentation becomes both urgent and fragile. Experience from past atrocity investigations shows that accountability often arrives years, sometimes decades, after violence ends. Whether justice is ever possible for victims in Iran will depend largely on whether credible evidence survives the present moment.
Yet this reality exposes an uncomfortable truth. The mechanisms available to respond to the Islamic Republic’s crackdown — fact-finding missions, sanctions, universal jurisdiction cases, and eventual prosecutions — are legally appropriate but painfully insufficient. They promise justice later while offering little protection now. As repression intensifies, the international system documents, condemns, and preserves evidence, but does not stop the violence.
This gap reflects a broader strain confronting the international order itself. At the World Economic Forum in Davos, Switzerland, Canadian Prime Minister Mark Carney warned that the stabilizing guardrails of the post-World War II system are weakening under geopolitical fragmentation. Weeks later in Munich, German Chancellor Friedrich Merz declared that the international order “as we have known it no longer exists.” Iran demonstrates what those warnings look like in practice: international institutions retain legal authority but struggle to produce timely protection when mass violence unfolds within sovereign borders.
This paradox is structural and should invite reflection and criticism rather than simple acceptance. The purported rules-based order provides pathways for accountability while simultaneously constraining the use of force that might halt atrocities. Article 2(4) of the U.N. Charter prohibits unilateral military action absent Security Council authorization or self-defense — a rule designed to prevent escalation and abuse by powerful States. The R2P principle does not create an independent legal basis for intervention, and geopolitical realities render Security Council authorization unattainable. The law therefore enables condemnation and future prosecution while largely foreclosing immediate coercive rescue.
This tension is not merely theoretical. The same legal framework that restrains interstate war can leave populations exposed to sustained internal violence. As atrocities mount, calls for intervention grow louder, yet legal analysis repeatedly reaches the same conclusion: military action justified solely by humanitarian concern would likely violate the U.N. Charter. Law operates here both as safeguard and constraint — preventing unlawful war while limiting the capacity to stop unlawful killing within a State engaged in repressing its own population.
Iran thus poses a defining question for the contemporary international system. If lawful responses amount primarily to documentation and delayed accountability, confidence in legal restraint itself may gradually erode. At the same time, loosening the prohibition on force risks returning to a world in which humanitarian rhetoric becomes a vehicle for geopolitical intervention, the very danger the U.N. Charter system was designed to prevent. The challenge, therefore, may not be choosing between law and protection, but confronting whether the present balance between them remains tenable in the face of mass atrocity.
The uncomfortable conclusion is that the system is not breaking down; it is functioning exactly as constructed. It prioritizes the prevention of catastrophic interstate war even when doing so limits the ability to halt catastrophic intrastate repression. The Iranian crisis reveals not a failure of international law, but the limits of a legal system designed to restrain force even when restraint carries profound human costs. If, however, the United States were to proceed with military action against Iran in circumstances inconsistent with the Charter, a different and equally serious challenge to law, legitimacy, and geopolitical stability could emerge — one that risks further weakening already strained legal norms governing the use of force.
