On October 21, 2025, Germany filed preliminary objections to the claims brought by Nicaragua against Germany at the International Court of Justice last year. Nicaragua alleges that Germany failed to prevent genocide in Gaza, failed to ensure respect for international humanitarian law (IHL) in Gaza, and indeed aided and assisted or was complicit in the commission of genocide and the violation of IHL in Gaza. For background on Germany’s arms transfers to Israel since October 2023, see here.
Germany’s preliminary objections are not publicly available but it is easy to guess what they say. During last year’s provisional measures proceedings, Germany did not argue that Israel complied with IHL in Gaza or even that Israel had not committed genocide in Gaza. Quite the contrary. Germany stunned some observers when it told the Court: “It is not a lack of funding that prevents humanitarian aid from reaching the Palestinian population. The real problem is the restrictions on the entry and distribution of humanitarian aid.” The restrictions in question were imposed by Israel.
Instead, Germany invoked the “indispensable third party” doctrine originating from the Court’s Monetary Gold case. According to this doctrine, the Court should not exercise jurisdiction over a claim brought by one State against a second State if resolving that claim would require the Court to determine the legal rights or responsibility of a third State not before the Court. According to Germany, the Court cannot resolve Nicaragua’s claims against Germany without determining the legal responsibility of Israel. Israel is not a party to the case. Hence, Germany argued, Nicaragua’s claims are inadmissible and the case should be dismissed.
Germany’s argument is misguided and the Court should reject it. Nicaragua’s claims against Germany are admissible and the case should proceed. Nicaragua’s claims do not depend on Israel’s legal responsibility, and the Court does not need to determine Israel’s legal responsibility to resolve Nicaragua’s claims. The Court needs to find only that Germany failed to prevent Israeli individuals from committing genocide, is complicit in the commission of genocide by Israeli individuals, or failed to ensure that Israeli individuals respect IHL. While Israel incurs legal responsibility as a State for the acts of its officials, Germany’s legal responsibility does not depend on Israel’s legal responsibility as a State. It follows that Israel is not an “indispensable third party.”
The Court’s case law is clear. The Court will decline to exercise its jurisdiction only if the legal rights or responsibility of a State not before it “would not only be affected by a decision, but would form the very subject-matter of the decision.” More precisely, the Court will decline to exercise its jurisdiction only if the legal responsibility of a State not before it is a logical prerequisite for the legal responsibility of the State before it. In contrast, the Court will exercise its jurisdiction even if the legal responsibility of a State not before it is a logical implication of the legal responsibility of the State before it. Israel’s legal responsibility may be a logical implication of Germany’s legal responsibility, but it is not a logical prerequisite for Germany’s legal responsibility. The “indispensable third party” doctrine does not apply, and Nicaragua’s claims are admissible.
The Duty to Prevent Genocide
The 1948 Convention on the Prevention and Punishment of the Crime of Genocide, as its name implies, is primarily concerned with preventing and punishing the crime of genocide. Article 1 confirms that genocide is a crime under international law which States undertake to prevent and to punish. It is axiomatic that only individuals commit crimes, and only individuals can be punished. In contrast, States commit internationally wrongful acts, for which they owe reparation. Article 2 defines genocide. Article 3 provides that genocide and related acts (conspiracy, incitement, attempt, complicity) are punishable. Again, only individuals can be punished. Article 4 refers to “persons committing genocide” or related acts. Article 5 refers to “persons guilty of genocide” or related acts. Article 6 refers to “persons charged with genocide” or related acts. Article 7 concerns extradition (of persons). The implication is clear. The legal duty to prevent genocide is, first and foremost, a legal duty to prevent individuals from committing genocide.
In 2007, the Court held for the first time that the Genocide Convention also imposes a legal duty on States not to commit genocide. In Bosnia and Herzegovina v. Serbia and Montenegro, the Court reasoned as follows:
the expressly stated obligation to prevent the commission of acts of genocide… requires the States parties, inter alia, to employ the means at their disposal … to prevent persons or groups not directly under their authority from committing an act of genocide or any of the other acts mentioned in Article III. It would be paradoxical if States were thus under an obligation to prevent, so far as within their power, commission of genocide by persons over whom they have a certain influence, but were not forbidden to commit such acts through their own organs, or persons over whom they have such firm control that their conduct is attributable to the State concerned under international law. In short, the obligation to prevent genocide necessarily implies the prohibition of the commission of genocide. (para. 166)
Simply put, a State’s legal duty to prevent individuals from committing genocide implies a State’s legal duty not to commit genocide itself. A State commits genocide when its officials or others under its effective control commit genocide. In that case, the individual commits a crime while the State commits an internationally wrongful act. Crucially, State responsibility does not displace individual responsibility. As the Court observed, “duality of responsibility,” responsibility of States and responsibility of individuals, “continues to be a constant feature of international law.”
The duty to prevent genocide remains, at its core, a duty to prevent individuals from committing genocide. This is plain from the Court’s finding that Serbia failed to prevent members of Bosnian Serb militias—whose acts were not attributable to any State—from committing genocide at Srebrenica. Importantly, the duty to prevent genocide is not limited by territory but instead applies to a State wherever it may be acting or may be able to act in ways appropriate to meeting its obligations (para. 183). Accordingly, a State has a legal duty to use its influence to prevent individuals in another State from committing genocide, including another State’s officials.
In most contexts, it is harmless to speak of a State’s duty to prevent another State from committing genocide. All this means is that one State has a duty to prevent certain individuals from committing genocide, and those individuals are officials of another State or under its effective control. In such cases, preventing those individuals from committing genocide also prevents the other State from committing genocide. However, speaking of a State’s duty to prevent another State from committing genocide should not obscure the fact that what is ultimately at stake is preventing individuals from committing genocide. The duty to prevent genocide works exactly the same way whether the individuals in question are private persons (including members of a non-State armed group) or officials of a State.
Germany has a legal duty to prevent Israeli officials over whom Germany has influence from committing acts of genocide. If Germany fails to use its influence, and those Israeli officials commit genocide, then Germany has breached its legal duty to prevent genocide in the same way that Serbia breached its legal duty to prevent genocide. Of course, Israel will also incur State responsibility for acts of genocide committed by its officials. But the Court does not need to find Israel responsible for those acts in order to find Germany responsible for failing to prevent those acts. The Court needs to find only that Israeli officials committed acts of genocide and that Germany failed to use its influence to stop them.
It follows that Israel is not an indispensable third party with respect to Nicaragua’s claim that Germany breached its legal duty to prevent Israeli officials from committing genocide in Gaza. Germany’s responsibility for failing to prevent genocide does not depend on Israel’s responsibility for committing genocide. It depends on Germany’s alleged failure to use its influence to prevent Israeli officials from committing genocide.
Put another way, Germany’s legal responsibility is not logically dependent on Israel’s legal responsibility. Consider the following propositions:
P1. Germany had a legal duty to use its influence to prevent Israeli officials from committing genocide.
P2. Germany failed to use its influence.
P3. Israeli officials committed genocide.
C1. Therefore, Germany breached its legal duty.
Of course, Israel’s legal responsibility is a logical implication of one ground of Germany’s legal responsibility (P3, above) and an additional true premise (P4, below):
P3. Israeli officials committed genocide.
P4. Israel is legally responsible for the acts of its officials.
C2. Therefore, Israel is legally responsible for genocide.
However, Israel’s legal responsibility (C2) is not a logical prerequisite of Germany’s legal responsibility (C1). It follows that Nicaragua’s claim (P1, P2, P3, C1) is admissible and should be adjudicated on its merits.
Aiding and Assisting Genocide versus Complicity in Genocide
Nicaragua also claims that Germany breached its obligations under the Genocide Convention “by providing aid, including military equipment, to Israel that would be used in the commission of genocide, by Israel.” This claim might be interpreted to allege that Germany aided or assisted the commission of genocide, or it might be interpreted to allege that Germany is complicit in the commission of genocide. These allegations may sound the same, but they may have different implications under the “indispensable third party” doctrine.
Under the law of State responsibility, a State which aids or assists another State in the commission of an internationally wrongful act is responsible for doing so if it knows the circumstances and is bound by the same legal obligation. Under this rule, the Court can find Germany responsible for aiding and assisting the commission of genocide in Gaza only if it first finds that another State (Israel) committed genocide in Gaza. Of course, Israel committed genocide in Gaza if and only if its officials (or other individuals under its effective control) committed genocide in Gaza. However, under this rule, the Court must decide whether Germany aided or assisted Israel’s commission of an internationally wrongful act. Germany’s State responsibility will depend on Israel’s State responsibility. Under the indispensable third party rule, the Court would at least have to postpone hearing this claim against Germany until it decides South Africa’s case against Israel.
It is plausible that customary international law has developed a broader rule precluding a State from aiding or assisting any subject of international law—another State, an international organization, a non-State armed group, or an individual—in the violation of international law (see here). On this view, if Germany aids or assists Israeli officials in the commission of genocide, then Germany’s responsibility would not depend on Israel’s responsibility and the “indispensable third party” doctrine would not apply. This is an attractive view, but there is a more straightforward way to interpret Nicaragua’s claim.
In its application instituting proceedings, Nicaragua referred to Germany’s obligations “to not aid and assist or be complicit in genocide.” Under the Genocide Convention, complicity in genocide is a “punishable” act committed by “persons” for which persons may be “charged” and found “guilty.” As the Court has observed, complicity “includes the provision of means to enable or facilitate the commission of the crime” and involves “a person providing aid or assistance to the direct perpetrators of the crime.” One person may be complicit in the commission of genocide by another person whether they are both State officials, both private individuals, or a mix of the two.
To say that a State is complicit in genocide is just to say that a State’s official, or a person under the State’s effective control, is complicit in the commission of genocide by another person who is neither the State’s official nor under the State’s effective control (see para. 179). It follows that Germany is complicit in genocide if German officials are complicit in the commission of genocide by individuals, namely by Israeli officials. Of course, if Israeli officials committed genocide, then Israel will incur State responsibility for the commission of genocide. But the Court does not need to find Israel responsible for genocide in order to find Germany complicit in genocide. The Court needs to find only that German officials were complicit in the commission of genocide by Israeli officials.
It follows that Israel is not an indispensable third party with respect to Nicaragua’s claim that Germany is complicit in the commission of genocide in Gaza. Germany’s responsibility for complicity in genocide does not depend on Israel’s responsibility for genocide. It depends on Germany’s officials providing “means to enable or facilitate” Israeli officials to commit genocide.
Again, Germany’s legal responsibility is not logically dependent on Israel’s legal responsibility. Consider the following propositions:
P1. Israeli officials committed genocide.
P2. German officials are complicit in Israeli officials’ commission of genocide.
P3. Germany is legally responsible for the acts of its officials.
C1. Therefore, Germany is legally responsible for complicity in genocide.
Of course, Israel’s legal responsibility is a logical implication of one ground of Germany’s legal responsibility (P1, above) and an additional true premise (P4, below).
P1. Israeli officials committed genocide.
P4. Israel is legally responsible for the acts of its officials.
C2. Therefore, Israel is legally responsible for genocide.
However, Israel’s legal responsibility (C2) is not a logical prerequisite of Germany’s legal responsibility (C1). It follows that Nicaragua’s claim (P1, P2, P3, C1) is admissible and should be adjudicated on its merits.
The Duty to Ensure Respect for International Humanitarian Law
Under Common Article 1 to the 1949 Geneva Conventions, States have a legal duty to ensure respect for the Conventions in all circumstances. Similar legal duties arise under customary IHL. States have both a negative obligation to not contribute to violations by others, and a positive obligation to do everything reasonably in their power to prevent violations by others (see here). At a minimum, States agreed that they must ensure respect for the Conventions by the whole population over which they exercise authority, including by private persons whose actions are not attributable to their State. In Nicaragua v. United States (1986), the Court found that Common Article 1 requires States to ensure respect for the Conventions by persons or groups involved in an armed conflict not of an international character on the territory of another State. Since then, the Court has repeatedly found that Common Article 1 requires States to ensure respect for the Conventions by other States (see here, here, and here).
The principle is clear. States have a legal duty to ensure that individuals respect the Conventions. Those individuals may be private persons, members of non-State armed groups, or officials of another State. The duty remains the same. Accordingly, Germany fails to ensure respect for the Geneva Conventions in Gaza if it contributes to violations by Israeli officials or fails to use its influence to prevent violations by Israeli officials. Of course, Israel is responsible for the acts of its officials, including for their failure to respect the Conventions. But the Court does not need to find that Israel failed to respect the Conventions. The Court only needs to find that Germany failed to ensure that Israeli officials respect the Conventions.
It is true that the Geneva Conventions impose legal obligations directly onto States as such (in contrast to the Genocide Convention, as explained above). At the same time, grave breaches of the Geneva Conventions are committed by persons, including by individual combatants and noncombatants, who must be brought to trial and face penal sanctions. Similarly, war crimes under customary international law are committed by individuals and incur individual criminal responsibility. The Geneva Conventions recognize that persons commit breaches of the laws and customs of war, and certain IHL rules expressly impose legal obligations directly on individuals. At a minimum, a State fails to ensure respect for the Geneva Conventions and customary IHL when it fails to use its influence to prevent individuals, including officials of other States, from committing grave breaches or war crimes under customary IHL, or from violating other IHL obligations addressed to them as individuals.
For its part, Nicaragua alleges that Germany failed to ensure respect for the Geneva Conventions with respect to grave breaches and “other war crimes.” In other words, Germany failed to use its influence to prevent Israeli officials from committing grave breaches and war crimes under customary IHL. Of course, Israel incurs State responsibility for acts of its officials that contravene both Israel’s legal obligations as a State and its officials’ legal obligations as individuals. But Germany’s failure to ensure that Israeli officials respect IHL does not depend on Israel’s responsibility as a State or the lawfulness of Israel’s actions as a State.
As before, Germany’s legal responsibility is not logically dependent on Israel’s legal responsibility. Consider the following propositions:
P1. Germany has a legal duty to ensure that Israeli officials respect IHL.
P2. Germany failed to use its influence.
P3. Israeli officials failed to respect IHL.
C1. Therefore, Germany breached its legal duty.
Of course, Israel’s legal responsibility is a logical implication of one ground of Germany’s legal responsibility (P3, above) and an additional true premise (P4, below).
P3. Israeli officials failed to respect IHL.
P4. Israel is legally responsible for the acts of its officials.
C2. Therefore, Israel is legally responsible for failing to respect IHL.
However, Israel’s legal responsibility (C2) is not a logical prerequisite of Germany’s legal responsibility (C1). It follows that Nicaragua’s claim (P1, P2, P3, C1) is admissible and should be adjudicated on its merits.
Conclusion
Israel is not an “indispensable third party” to the case brought by Nicaragua against Germany. Nicaragua’s central claims against Germany—failure to prevent genocide, complicity in genocide, and failure to ensure respect for IHL—do not require the Court to determine whether Israel has committed genocide or violated IHL. Instead, these claims require the Court to determine whether Israeli officials have committed genocide or violated IHL. While the acts of Israeli officials are imputable to Israel, the Court need not impute these acts to Israel in order to resolve Nicaragua’s claims. Israel’s legal responsibility is not a logical prerequisite of Germany’s legal responsibility, and Israel’s legal responsibility does not form the “very subject matter” of the case against Germany. The case should proceed, and the Court should decide whether or not Germany breached its legal obligations to prevent genocide and ensure respect for IHL in Gaza.
