The crime of aggression is the planning, preparation, initiation, or execution of an illegal war by a person in a position to control a state’s political or military action. It is defined in Article 8 bis of the Rome Statute and sits alongside genocide, crimes against humanity, and war crimes as one of the four offenses within the International Criminal Court’s jurisdiction. Penalties run up to life imprisonment. The ICC’s authority to prosecute the crime only activated on July 17, 2018, and no individual has yet been formally charged with it before the court, which is why the definition and the court’s narrow reach both matter when the term comes up in headlines.
What Article 8 bis Actually Prohibits
Article 8 bis has two layers. The outer layer is the “crime of aggression” itself: the planning, preparation, initiation, or execution of an act of aggression by someone in a position to effectively control or direct the political or military action of a state. The inner layer is the “act of aggression”: the use of armed force by one state against the sovereignty, territorial integrity, or political independence of another, in a manner inconsistent with the UN Charter.1International Committee of the Red Cross Databases. Amendment to the Rome Statute of the International Criminal Court on the Crime of Aggression – Article 8bis
Not every illegal use of force qualifies. The act must amount to a “manifest violation” of the UN Charter, judged on three factors together: character, gravity, and scale. Character looks at the nature and purpose of the operation. Gravity measures the intensity of force and the damage caused. Scale considers the size of the forces and the geographic reach. A formal understanding adopted at the 2010 Kampala Review Conference confirmed that no single factor is enough on its own.
The threshold is deliberately high. A minor border incident, an accidental incursion, or an isolated strike with limited consequences does not rise to a manifest violation even if cross-border force was used. Contested categories like certain humanitarian interventions or counterterrorism operations occupy a legal gray area, and the manifest standard is designed to keep those disputes out of a criminal courtroom. Only clear, large-scale armed aggression was intended to trigger individual criminal liability.
Which Military Acts Count as Aggression
Article 8 bis incorporates a list of qualifying acts drawn from UN General Assembly Resolution 3314. These are the concrete state actions that can form the basis of a prosecution:
- Invasion, military occupation however brief, or annexation of another state’s territory by force.1International Committee of the Red Cross Databases. Amendment to the Rome Statute of the International Criminal Court on the Crime of Aggression – Article 8bis
- Bombardment of another state’s territory with any weapons, including airstrikes, missiles, or artillery.
- Blockade of the ports or coasts of another state by armed forces.
- An attack on the land, sea, or air forces of another state.
- Use of military forces stationed in another state’s territory with its agreement in a way that breaches the terms of that agreement, or keeping them there after it expires.
- Allowing your territory to be used by another state to carry out an act of aggression against a third country.
- Sending armed bands, irregular fighters, or mercenaries to conduct armed attacks against another state serious enough to amount to the acts listed above.2University of Minnesota Human Rights Library. Definition of Aggression – UN General Assembly Resolution 3314
The last two provisions matter because they close an obvious loophole. A country that funds mercenary groups to invade a neighbor, or that lends its airfields to another state’s offensive, faces the same legal exposure as one that sends its own uniformed military.
Who Can Be Charged
Unlike every other crime in the Rome Statute, the crime of aggression can only be charged against senior leaders. Article 8 bis restricts liability to a person “in a position effectively to exercise control over or to direct the political or military action of a State,” and Article 25(3 bis) confirms that the general rules on individual criminal responsibility apply only to persons meeting that threshold.3International Criminal Court. Rome Statute of the International Criminal Court
In practice, this means heads of state, defense ministers, foreign ministers, and senior military commanders with real strategic authority. A mid-ranking officer following orders or a bureaucrat in a supporting role does not meet the standard, even if they participated in an operation later found to be aggression. The prosecution has to show the defendant personally held enough power to shape the decision to use force.
Lower-ranking personnel are not off the hook for everything that happens during an illegal war. War crimes and crimes against humanity apply across the chain of command. The leadership clause only limits the specific charge of aggression to those at the top who chose to start the conflict.
When Force Is Lawful Instead
Two recognized justifications can take a use of force outside the definition. A third is sometimes raised but has no firm legal footing.
Security Council Authorization
Under Chapter VII of the UN Charter, the Security Council can authorize military action when it determines there is a threat to peace, a breach of peace, or an act of aggression. Article 42 lets the Council approve armed force when non-military measures have proven inadequate.4United Nations. Chapter VII: Action with Respect to Threats to the Peace, Breaches of the Peace, and Acts of Aggression Operations carried out under a valid Council resolution are lawful under the Charter, so the manifest violation element cannot be satisfied.
Self-Defense
Article 51 of the UN Charter preserves a state’s inherent right to use force in individual or collective self-defense if an armed attack occurs. The right is not unlimited. It applies only until the Security Council takes measures to address the threat, and states must immediately report their defensive actions to the Council.5United Nations. Repertory of Practice of United Nations Organs – Article 51 The response also has to be necessary and proportionate. A state that invoked self-defense to justify a full-scale invasion well beyond what the original attack warranted could still face scrutiny under the manifest violation standard.
Humanitarian Intervention
Some states and scholars have argued that force used to stop an ongoing atrocity should not count as aggression even without Security Council authorization. This argument has no firm legal footing. The prevailing view is that unilateral humanitarian intervention violates Article 2(4) of the UN Charter, which prohibits the use of force against another state’s territorial integrity. Because that prohibition is treated as a peremptory norm of international law, no defense of necessity overrides it. The vast majority of states have formally rejected the existence of a legal right to unilateral humanitarian intervention, and a leader who ordered such an operation could face aggression charges if the military action met the manifest violation threshold.
How the ICC Can Actually Prosecute
The ICC’s jurisdiction over aggression is the most restricted of any crime in the Rome Statute. Three mechanisms can trigger a case, but each comes with constraints that do not apply to genocide, war crimes, or crimes against humanity.
Triggering an Investigation
An investigation can begin through a referral by the UN Security Council, a referral by a state party, or the Prosecutor acting on their own initiative.6International Committee of the Red Cross. Rome Statute of the International Criminal Court – Article 13 For the last two routes, the Prosecutor must first notify the UN Secretary-General and check whether the Security Council has already determined that an act of aggression occurred. If no determination comes within six months, the Prosecutor can proceed only with authorization from the Pre-Trial Division.7United Nations. Rome Statute Amendments on the Crime of Aggression – Article 15 bis The Security Council can also suspend any investigation for 12 months under Article 16 of the Rome Statute.
The Kampala Jurisdictional Limits
The Kampala Amendments created rules for aggression that are much narrower than those for other ICC crimes:
- The ICC cannot exercise jurisdiction over the crime of aggression when it is committed by nationals of a non-state party or on its territory, unless the Security Council refers the situation.3International Criminal Court. Rome Statute of the International Criminal Court
- Even states that have ratified the Rome Statute can file a declaration opting out of the court’s jurisdiction over aggression. The declaration can be withdrawn at any time.7United Nations. Rome Statute Amendments on the Crime of Aggression – Article 15 bis
- The court generally cannot exercise jurisdiction over aggression unless the state involved has ratified the Kampala Amendments specifically, not just the original Rome Statute.
The practical effect is large. Major military powers including the United States, Russia, and China are not parties to the Rome Statute at all, and many Rome Statute members have not ratified the Kampala Amendments. New ratifications continue to come in, but the number of states covered remains limited.8United Nations Treaty Collection. Amendments to the Rome Statute on the Crime of Aggression – Status Without a Security Council referral, the ICC’s reach is largely confined to acts committed by or against the relatively small group of states that have both joined the Rome Statute and ratified its aggression amendments. Because the five permanent Council members each hold a veto, referrals involving those states are effectively impossible.
Penalties and Timing
A conviction can result in imprisonment of up to 30 years, or life imprisonment when the extreme gravity of the crime and the defendant’s individual circumstances justify it. The court can also impose fines and order the forfeiture of assets derived from the crime, with forfeited property potentially transferred to the Trust Fund for Victims.9United Nations. Rome Statute – Part 7 Penalties There is no statute of limitations. Article 29 of the Rome Statute bars any time limit on prosecuting the crimes within the court’s jurisdiction, so a leader who planned or launched a war of aggression can be charged years or decades after the fact.10Office of the United Nations High Commissioner for Human Rights. Rome Statute of the International Criminal Court That matters most for eventual transitions of power, exile, or regime change.
Prosecution Outside the ICC
The ICC’s narrow jurisdiction has pushed attention toward alternative routes, chiefly special tribunals and, in principle, domestic courts.
The most prominent current effort is the Special Tribunal for the Crime of Aggression Against Ukraine, being established through the Council of Europe. Because Russia is not a party to the Rome Statute, the ICC cannot prosecute Russian leaders for aggression without a Security Council referral, which Russia’s veto blocks. The Core Group working on the tribunal concluded its work on the necessary legal instruments in March 2025, and the bilateral agreement between Ukraine and the Council of Europe was signed on June 25, 2025. As of early 2026, the European Union is contributing 10 million euros to a Council of Europe project preparing the tribunal’s institutional foundations.11Council of Europe. Special Tribunal for the Crime of Aggression against Ukraine – Frequently Asked Questions The tribunal’s jurisdiction rests on Ukrainian territorial jurisdiction, it is complementary to the ICC (which has primacy if a suspect is in ICC custody), and it features a roster of 15 judges elected for nine-year terms. Sitting heads of state and foreign ministers keep their immunity unless they leave office or it is waived. Trials in absentia are possible when all reasonable steps to secure the defendant’s presence have failed.
Domestic prosecution is theoretically available but rare. The Kampala Review Conference clarified that the amendments create no obligation for any state to exercise domestic jurisdiction over acts of aggression committed by another state. A small number of countries have nonetheless established universal jurisdiction over the crime, including Austria, Cyprus, Georgia, Liechtenstein, Luxembourg, the Netherlands, North Macedonia, Samoa, and Slovenia. In practice, domestic prosecution faces severe obstacles: head-of-state immunity, the difficulty of obtaining custody over a foreign leader, and the political sensitivity of one state’s courts judging another’s decision to go to war. No domestic court has successfully prosecuted anyone for the crime of aggression in the modern era.