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Cross Judicial Fertilization

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Cross-Judicial Fertilization: The Use of Foreign precedents by Constitutional Judges


Les travaux de ce groupe de recherche are published in English. It is well understood that it is possible to present the contributions in French.

Research Project Description

Originally established at the 2007 World Congress (Athens, Greece) by Tania Groppi and Marie-Claire Ponthoreau, the Interest Group on “Cross-Judicial Fertilization. The Use of Foreign Precedents by Constitutional Judges” has already addressed the use of foreign precedents in constitutional interpretation (at the 2010 World Congress in Mexico City), the use of foreign law in constitution-making and amending endeavors (2014 World Congress in Oslo, Norway), and explored the role played by foreign legal sources in post-conflict and in-conflict conditions (2018 World Congress in Seoul, South Korea).


In 2021, the Group launched a new research project on the use of foreign precedents by Constitutional Judges in the XXI Century, with the aim to contribute to the next World Congress to be held in Johannesburg (South Africa) in December 2022.


The “original” research project surveyed the use of foreign precedents by Supreme and Constitutional Courts in deciding constitutional cases in 16 countries. Its purpose was to determine – through an empirical analysis, built on both quantitative and qualitative indicators – to what extent foreign case law is cited and the reliability of studies describing and reporting instances of “trans-judicial dialogue” between Courts. Some of the contributions were published in T. Groppi, M.-C. Ponthoreau (eds), The Use of Foreign Precedents by Constitutional Judges, Hart Publishing, 2013.


The purpose of the new research project launched in 2021 is to update, supplement and complete the aforementioned research. The project now encompasses 44 different countries, covering the period from 2011 to 2021. Quantitative and qualitative data for those countries that had already been surveyed in the first research project will now be updated, and 28 “new” countries, originally not included, will now become part of this new iteration of the project.


The Group considers that in the last decade the use of foreign precedents by constitutional judges has become an even more central argument in constitutional reasoning, in parallel with the growing impact of the ICT on the judicial activity and with the expansion of the trans-judicial communication. .


Currently composed by 50 members, the Interest Group features the participation of scholars from several African, American, Asian, European, Latin American and Oceania countries, representing jurisdictions belonging to both Common law and Civil law traditions, and countries relying on both centralized and decentralized systems of judicial review.


Inter-American Academy of Human Rights

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University of Siena

University of Bordeaux

University of Sussex



Contact information

For more information on the Interest Group, its activities and research, you may want to contact the dedicated email address ( ).
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