General Principle

The establishment of international criminal tribunals creates the problem of coordinating their action with that of national courts.  This problem is manifest when both international and national courts are empowered to prosecute the same crimes.  Deciding which courts take precedence raises difficult questions of sovereignty and international relations.  Clear guiding principles are necessary to resolve the delicate issue of whether an international or national court takes priority in given case.  The principle of complementarity provides such guidance.

The principle of complementarity embodies the concept that a court may only assert jurisdiction over a case that another court has not already investigated or prosecuted.  The subsidiary court generally enjoys priority in the exercise of jurisdiction over a case, and the chief court only exercises its complementary jurisdiction in exceptional circumstances.  In international law, the concept of complementarity primarily applies in the context of the exercise of jurisdiction by the International Criminal Court.

The Jurisdiction of the ICC

The International Criminal Court is the first standing tribunal empowered to prosecute violations of international humanitarian law.  The permanent and universal nature of the ICC distinguishes it from similar, temporary judicial bodies, such as the International Criminal Tribunal for the Former Yugoslavia. The Rome Statute of the International Criminal Court, which established the ICC, was adopted on July 17, 1998 by a treaty, following a conference convened by the U.N. General Assembly.  The ICC is located at The Hague in the Netherlands.

The ICC does not prosecute most major crimes of international concern.  Its jurisdiction is limited to crimes of genocide, crimes against humanity, war crimes, and the crime of aggression.  Article 6 of the Rome Statute defines genocide as follows: “any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group as such: (a) killing members of the group; (b) causing serious bodily or mental harm to members of the group; (c) deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; (d) imposing measures intended to prevent births within the group; (e) forcibly transferring children of the group to another group.”  Article 7 of the Rome Statute contains a list of specified acts that constitute crimes against humanity.  Some of these acts include murder, extermination, enslavement, torture, rape, and persecution.  Article 8 of the Rome Statute provides a detailed list of war crimes subject to prosecution before the ICC, which includes serious breaches of the Geneva Conventions.  Finally, the Rome Statute does not define the crime of aggression.  Thus, the ICC will not be able to prosecute this crime until the Rome Statute has been amended to define it properly.

The jurisdiction of the ICC may be invoked in three ways.  First, a party may refer an alleged crime to the ICC Prosecutor.  Second, the U.N. Security Council may refer alleged crimes to the ICC Prosecutor.  And third, the ICC Prosecutor may initiate an investigation into an alleged crime.  But under the first and third avenues listed above, the ICC may only exercise jurisdiction if the state on whose territory the conduct occurred or the state of the nationality of the accused person is a party to the Rome Statute.  Notably, many world powers are not parties to the Rome Statute.  These nations include China, Egypt, India, Indonesia, Iran, Pakistan, Russia, and the United States.  Nonparty states may, however, accept the jurisdiction of the ICC ad hoc.     

Complementarity and the Jurisdiction of the ICC

The jurisdiction of the ICC is further limited by the concept of complementarity.  Unlike ad hoc criminal tribunals like the ICTY and the ICTR, the ICC acts in a role complementary to national criminal jurisdictions.  Reasons for this unique organization include limiting the number of cases referred to the ICC and respecting national sovereignty.  The principle of complementarity is spelled out in paragraph 10 of the Preamble to the Rome Statute and in Articles 1, 15, 17, 18, and 19 of the Rome Statute.

Under the principle of complementarity, the ICC is barred from asserting jurisdiction over a crime whenever a national court exercises its jurisdiction over the crime and one of the following conditions is met: (i) the state has jurisdiction under its national law; (ii) the case is being investigated or prosecuted by the state’s authorities, or those authorities have properly decided not to prosecute; (iii) the case is not of sufficient gravity to justify action by the ICC.  Thus, under the principle of complementarity, the ICC defers to a state’s exercise of jurisdiction over one of the crimes enumerated in the Rome Statute.  But under the principle of complementarity, the ICC may assert jurisdiction over one of those crimes even if a case concerning the crime is pending before national courts.  For the ICC to do so, two conditions must be met.  First, the ICC may exercise jurisdiction where the state is unable or unwilling genuinely to carry out the investigation or prosecution.  This justification for the exercise of ICC jurisdiction includes decisions by national authorities not to prosecute where that decision results from the state’s unwillingness or inability genuinely to prosecute the crime.  And second, the case must be of sufficient gravity to justify the exercise of the ICC’s jurisdiction.

Because the ICC may only override national criminal jurisdiction when national authorities are “unable” or “unwilling” to investigate and prosecute, the essence of the principle of complementarity lies in the definition of those terms.  Under Article 17 of the Rome Statute, a nation is “unwilling” when: (i) national authorities are shielding the accused from criminal responsibility; or (ii) national authorities have unduly delayed the proceedings, manifesting an intent to not bring the accused to justice; or (iii) the national proceedings are not conducted independently or impartially, manifesting an intent to circumvent justice.  In addition, a nation is “unable” to prosecute when, primarily as a result of the collapse of its judicial system, it is not in a position to: (i) detain the accused or have him surrendered by the authorities holding him in custody; or (ii) collect the necessary evidence; or (iii) carry out criminal proceedings.  The principle of complementarity applies regardless of the manner in which ICC proceedings are initiated, whether by a state party, the U.N. Security Council, or the ICC Prosecutor. 

The principle of complementarity found in the Rome Statute of the ICC ensures respect for national judicial systems and incentivizes them to operate in a fair and effective manner.  It both empowers the ICC and carefully limits that power.  Guided by the principle of complementarity, the ICC investigates and prosecutes international crimes when a domestic legal system cannot or will not, expanding the reach of justice on the world stage.

Sources:

Anthony Aust, Handbook of International Law (2005).

Ian Brownlie, Principles of Public International Law, 6th ed. (2003).

Thomas Buergenthal, Dinah Shelton & David P. Stewart, International Human Rights in a Nutshell, 4th ed. (2009).

Antonio Cassese, International Criminal law (2003).