The Principle of Complementarity: When Do States Take the Lead?

In the realm of international law and global governance, the principle of complementarity stands as a cornerstone of how justice is administered across borders. Rooted in the operations of the International Criminal Court (ICC), complementarity is more than a legal doctrine—it’s a balancing act between national sovereignty and international intervention. It seeks to empower states to pursue justice while allowing international bodies to intervene when national systems falter.

This principle is most visible in international criminal justice, where the ICC operates only when a state is “unable or unwilling” to prosecute serious crimes like genocide, war crimes, or crimes against humanity. However, the idea of complementarity has far-reaching implications beyond just criminal law. It touches on human rights, humanitarian interventions, environmental governance, and even economic policy coordination.

But when do states actually take the lead under this principle? What motivates them to act first—or at all—before international bodies intervene? In this blog, we’ll explore the dimensions of complementarity, the factors that determine state leadership, and the practical implications in global governance.

Understanding the Principle of Complementarity

Origin and Legal Framework

The principle of complementarity is codified in Article 17 of the Rome Statute, which established the ICC. It asserts that the Court is a court of “last resort,” designed to complement, not replace, national judicial systems. If a state is genuinely investigating or prosecuting a case, the ICC must defer to the national proceedings.

This legal architecture serves a dual purpose: respecting state sovereignty and ensuring accountability for grave international crimes. The ICC intervenes only when there’s a “failure of justice” at the national level—meaning the state is either unwilling or genuinely unable to carry out the process.

Complementarity as a Governance Strategy

Beyond the courtroom, the principle functions as a broader governance strategy. It incentivizes states to develop their legal and institutional capacities. By stepping up to handle their own cases, states can avoid international scrutiny while demonstrating a commitment to rule of law.

Areas where States Take the Lead?

When There’s Political Will and Institutional Capacity

At the heart of successful national prosecutions lies political will. When governments are committed to justice—whether out of genuine concern or the need to legitimize their rule—they are more likely to initiate investigations and prosecutions themselves.

Institutional capacity is equally vital. A state must have functioning courts, impartial judges, effective law enforcement, and the ability to ensure witness protection. States like Colombia and Uganda have taken significant steps in handling transitional justice through national systems, supported but not overtaken by international actors.

Case Example: In Colombia, the Special Jurisdiction for Peace (JEP) was set up as part of a peace deal with the FARC. The process reflects the state’s initiative to address crimes committed during the conflict, reducing the need for ICC intervention.

To Preempt International Intervention

States sometimes act swiftly to prosecute crimes in order to prevent international bodies from stepping in. This is especially true when leaders want to avoid the reputational damage that comes from being subject to international investigations.

Example: Kenya, after the post-election violence of 2007-08, attempted to establish national tribunals to try the perpetrators. Though eventually the ICC stepped in due to lack of progress, the initial efforts were a clear attempt to preempt intervention.

Under Pressure from Civil Society and International Partners

Domestic and international pressure can push states to take the lead. Civil society organizations often play a key role in demanding accountability, filing cases, or exposing failures in governance.

International donors and allies may also tie aid or political cooperation to rule-of-law benchmarks. This kind of pressure can catalyze action even in reluctant states.

Example: In the Central African Republic, civil society and international donors lobbied the government to create the Special Criminal Court, a hybrid tribunal that works in tandem with the ICC.

As a Sovereignty Strategy

Taking the lead in legal processes allows states to assert their sovereignty. This is especially important for post-colonial states sensitive to foreign intervention. By conducting their own investigations, these states send a message: “We are capable of handling our own affairs.”

Example: South Africa has invoked the principle of complementarity to argue against ICC overreach in some cases, highlighting the capacity of its judiciary.

When National Interest Aligns with Justice

There are times when pursuing justice also aligns with political or strategic interests. A state might use prosecutions to discredit political opponents, consolidate power, or curry favor with international allies.

While this is not an ideal application of the principle, it nonetheless results in state-led action—albeit not always fair or impartial.

Example: In Rwanda, the post-genocide government pursued widespread prosecutions through Gacaca courts. While these efforts demonstrated national leadership, they were also instrumental in consolidating the Rwandan Patriotic Front’s control.

Barriers to State Leadership in Complementarity

Lack of Capacity

Some states simply lack the resources, expertise, or institutional infrastructure to prosecute serious crimes. This includes lack of trained judges, forensic resources, and security for witnesses or prosecutors.

In such cases, even if there is willingness, inability triggers ICC jurisdiction.

. Political Interference and Corruption

In many contexts, the very individuals who should be prosecuted are part of the ruling elite. This creates a massive conflict of interest. Political interference and lack of judicial independence remain critical obstacles to genuine national proceedings.

Example: In Sudan, while the transitional government has pledged to cooperate with the ICC, internal power struggles and fears of backlash have hindered meaningful progress.

Fragile or Post-Conflict Environments

States emerging from conflict may lack the stability needed to carry out complex legal proceedings. Rebuilding trust in institutions, ensuring security, and dealing with humanitarian crises often take precedence over legal accountability.

The Role of the International Criminal Court

 Catalyst for Domestic Action

Ironically, the threat of ICC action often motivates states to take the lead. The court acts as a backstop, prompting domestic reforms or investigations that might not have occurred otherwise.

This is sometimes called “positive complementarity,” where the ICC plays a supportive rather than a confrontational role. The ICC can offer training, legal guidance, and technical assistance to strengthen domestic capacity.

Last Resort, Not First Choice

The ICC’s intervention is supposed to be exceptional. When it steps in, it often means the national system has utterly failed. However, reliance on the ICC is no panacea. The court has limited reach, resources, and jurisdiction, and it operates in a highly politicized environment.

Expanding Complementarity Beyond the ICC

In Human Rights and Transitional Justice

The logic of complementarity also applies to broader justice processes like truth commissions, reparations programs, and institutional reforms. These mechanisms, when initiated by the state, reinforce national ownership of justice and reconciliation.

 In Environmental and Health Governance

Complementarity also surfaces in climate governance and public health. For instance, states take the lead in implementing international environmental treaties or responding to pandemics, with organizations like the UN or WHO stepping in only when national systems fail.

 In Regional Legal Systems

Regional courts, such as the African Court on Human and Peoples’ Rights or the European Court of Human Rights, often rely on complementarity. They assess whether states have exhausted all national remedies before they accept a case.

Evaluating the Effectiveness of Complementarity

 Success Stories

* **Colombia** – Used the principle to strengthen domestic justice mechanisms during peace processes.

* **Rwanda** – Despite criticism, the use of Gacaca courts reflected national ownership.

* **Uganda** – Combined ICC involvement with traditional justice mechanisms for the Lord’s Resistance Army conflict.

Limitations and Criticisms

Selective Application – Powerful States or Allies Often Escape Scrutiny, Undermining the Credibility of Complementarity

One of the most frequently cited criticisms of the principle of complementarity is its selective application, particularly when it comes to powerful states or those with strong geopolitical allies. The ICC and other international mechanisms often face accusations of disproportionately targeting weaker or less politically influential states while overlooking violations committed by more powerful nations. This perception is not unfounded.

Take, for instance, the criticism that the ICC has historically focused largely on African states, even though serious international crimes have occurred elsewhere. While there have been preliminary investigations in situations involving Western or powerful countries—such as the United States’ conduct in Afghanistan or Israel’s actions in Gaza—few, if any, of these have progressed to full investigations or prosecutions. The U.S., which is not a party to the Rome Statute, has also exerted pressure on the Court, including the imposition of sanctions against ICC officials under the Trump administration. This not only inhibits the ICC’s operational independence but also sends a message that powerful states can effectively evade accountability mechanisms.

This double standard deeply undermines the legitimacy and credibility of complementarity. If the principle is meant to apply universally, then exceptions based on power politics erode trust in the international justice system. States that see the ICC and the complementarity principle as biased or selectively applied are less likely to cooperate or take their own judicial responsibilities seriously. This ultimately dilutes the deterrent and moral authority that the system seeks to uphold.

Selective application also impacts domestic public perception. Citizens in countries subject to ICC scrutiny often question why global powers are not held to the same standards. This undermines domestic confidence in international cooperation and fosters a narrative of neocolonialism or legal imperialism. In this context, complementarity risks being viewed not as a fair legal doctrine but as a tool of geopolitical control.

To preserve the integrity of complementarity, consistent application is vital. Efforts must be made to address crimes regardless of the political clout of the actors involved. Otherwise, the principle fails in its core purpose: to ensure justice is served when national systems do not or cannot act.

State Abuse of the Principle – Governments May Fake Compliance to Avoid ICC Jurisdiction Without Genuine Intent to Prosecute

A subtler but equally dangerous threat to the principle of complementarity is state abuse—when governments perform superficial or symbolic acts of judicial engagement to avoid ICC scrutiny without any genuine intent to deliver justice. These performative gestures may include opening investigations with no real progress, launching politically motivated prosecutions of low-level perpetrators, or creating “special commissions” that serve more as PR strategies than justice mechanisms.

This type of abuse exploits the very spirit of complementarity, which assumes good faith on the part of states. The Rome Statute requires that national proceedings be genuine, not merely procedural. However, assessing the sincerity of domestic efforts is inherently difficult and often becomes a politically charged process. Governments facing possible ICC intervention may initiate token investigations or manipulate evidence just enough to claim they are fulfilling their obligations.

Such manipulation creates legal and diplomatic gray areas. If the ICC disputes a state’s claim of genuine action, it risks being accused of infringing on sovereignty. If it accepts the claim without scrutiny, it potentially allows impunity to persist. This dilemma makes enforcement of complementarity both politically sensitive and legally complex.

A notable example can be seen in Kenya’s response to the post-election violence of 2007–08. Following initial reluctance to prosecute high-level political actors domestically, the government resisted ICC involvement by proposing national trials. However, progress was slow, and many believed the initiatives were designed more to deflect international pressure than to achieve justice. Eventually, the ICC proceeded with cases, but they collapsed due to witness interference and lack of state cooperation.

This type of abuse also sets a negative precedent. Other governments may see that minimal action can be sufficient to avoid international scrutiny, especially if there are no consequences for deception. In doing so, the principle of complementarity becomes not a mechanism for accountability but a shield for inaction.

To counter this, international bodies need stronger tools for assessing and verifying the genuineness of domestic proceedings. They must also hold states accountable when clear patterns of manipulation or insincerity emerge. Otherwise, the principle risks becoming a procedural loophole instead of a safeguard for justice.

Structural Inequalities – Weaker States May Be Subject to Complementarity Pressures That Stronger States Can Resist

The global legal system, much like the global political order, is shaped by structural inequalities that affect how laws are applied and enforced. Under the principle of complementarity, these inequalities manifest in the uneven pressure placed on weaker states—those with limited political influence, economic power, or institutional capacity. Meanwhile, stronger states often escape such pressures due to their leverage in international politics or their ability to shield themselves through diplomacy, alliances, or legal exceptions.

Complementarity presupposes that all states are equal participants in the international justice system. However, in reality, not all states have equal resources to establish or reform judicial systems, investigate crimes, or provide legal safeguards for victims and witnesses. The burden of proving “willingness” and “ability” to prosecute serious crimes becomes disproportionately heavier for states emerging from conflict, dealing with economic crises, or facing political instability. Even when these states want to take the lead, they may not have the means to do so effectively.

In contrast, powerful states can leverage their geopolitical status to delay or prevent investigations into their actions or those of their allies. This is compounded by the fact that some major powers, such as the United States, Russia, and China, are not parties to the Rome Statute, giving them legal immunity from ICC jurisdiction unless referred by the UN Security Council—a body where they hold veto power. This structural imbalance creates a two-tiered system of justice: one for the powerful and another for the vulnerable.

The implications are profound. Weaker states may be seen as easy targets for ICC action, reinforcing narratives of international justice being selective or neocolonial. This erodes confidence in global institutions and discourages genuine engagement from affected populations. It also affects how complementarity is perceived—not as a fair doctrine that empowers states, but as a burden that disproportionately falls on the shoulders of those least equipped to bear it.

Moreover, donor-driven justice reforms, often imposed on weaker states, can distort national priorities and erode local ownership of the justice process. External funding tied to justice benchmarks may push fragile governments to pursue cases simply to satisfy international partners, not because of internal political will or grassroots demand.

Addressing these inequalities requires a rethinking of complementarity not just as a legal principle, but as part of a broader framework for equitable international cooperation. It means investing in national capacity building, ensuring equitable application of international law, and holding all states—regardless of power—accountable for their actions. Only then can complementarity function as a truly balanced and just principle in global governance.

Conclusion

The principle of complementarity is both a legal doctrine and a political negotiation. It hinges on the assumption that states should, and can, lead in administering justice—particularly in serious international crimes. But in practice, the conditions under which states actually take the lead are complex and contingent on political will, capacity, external pressure, and strategic calculations.

Complementarity reflects an ideal of cooperative justice—where national systems function as the primary arena for accountability, with international bodies stepping in only when necessary. When it works well, it promotes local ownership, builds trust in institutions, and reinforces the rule of law. When it fails, it exposes the limitations of both national and international systems.

As global justice continues to evolve, the principle of complementarity remains essential. Its future will depend not only on legal frameworks, but on the willingness of states to genuinely commit to justice—and the ability of international institutions to support and challenge them when they do not.

First author : tushar kaushik , 2nd semester , SRM university , LLM , Delhi NCR , sonipat , haryana

Second author : Dr. Anjali dixit , associate professor , faculty of law, SRM university , Delhi NCR , Sonipat, Haryana .