Complementarity in the Rome Statute: from theory to practice


Background research project on Complementarity

The principle of complementarity is one of the cornerstones of the architecture of the Rome Statute. It shapes various dimensions of ICC and domestic practice, ranging from prosecutorial strategy and criminal policy to statutory implementation and compliance.

The operation of complementarity is of paramount importance for the operation and impact of international criminal justice. International courts and tribunals are only able to accomplish their mandates and leave a 'lasting footprint' on society, if they manage to mobilise support and genuine justice efforts at the domestic level.  

Traces of complementarity are replicated in the relationship between the ad hoc tribunals and domestic jurisdiction (Rule 11 bis), the exercise of universal jurisdiction ('horizontal complementarity') and the operationalisation of the concept of "Responsibility to Protect".

One of the dilemmas of complementarity is that many of its theoretical underpinnings and operational features are underdeveloped. The Rome Statute sets out the general contours of the concept in three paragraphs (Article 17). The existing text leaves a considerable degree of ambiguity and space for creative interpretation.

The concept has thus undergone dynamic transformation. The Office of the Prosecutor has developed guidelines and policy principles on complementarity. Other aspects have been clarified by the jurisprudence of the Court in the context of the first situations under investigation. Some of these conceptions deviate from classical understandings of complementarity. Core notions ("gravity", "inability", "case") and key concepts (self-referrals, primacy of domestic jurisdictions, 'positive complementarity') are at the heart of judicial and policy debate.

The broader implications of complementarity in international relations and domestic societies are not yet well understood and researched. Implementation remains a challenge, both in terms of law and policy.

Project Background

Project goals

Research themes

Conference report






Contributors to the research project include:

Ass. Prof. Carsten Stahn, Leiden University

Dr. Mohamed El Zeidy, International Criminal Court

Ass. Prof. William Burke-White, University of Pennsylvania

Ass. Prof. Hector Olasolo, University of Utrecht

Enrique Carnero, International Criminal Court

Dr. Rod Rastan, International Criminal Court

Ass. Prof. Darryl Robinson, Queens University Canada

Prof. Frederic Megret, McGill University

Ass. Prof. Jann Kleffner, University of Amsterdam

Dr. Jo Stigen, University of Oslo

Prof. Megan Fairlie, Florida International University

Joseph Powderly, National University of Ireland

Prof. Harmen van der Wilt, University of Amsterdam

Dr. Olympia Bekou, University of Nottingham

Morton Bergsmo, Peace Research Institute Oslo

Prof. Roger Clark, Rutgers University

Prof. Mark Drumbl, Washington and Lee University

David Tolbert, Special Tribunal for Lebanon

Ass. Prof. Bacle Don Taylor III, St Louis, Washington University

Fidelma Donlon, National University of Ireland

Dr. Cedric Ryngaert, University of Leuven & Utrecht

Paul Seils, United Nations

Prof. William Schabas, National University of Ireland

Prof. Kai Ambos, University of Gvttingen

Prof. Robert Cryer, University of Birmingham

Sarah Nouwen, University of Cambridge

Dr. Marlies Glasius, University of Amsterdam

Christopher Hall, Amnesty International






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