Originally established in the 2007 World Congress (Athens, Greece), the Interest Group on “Cross-Judicial Fertilization. The Use of Foreign Precedents by Constitutional Judges” already worked on the use of foreign precedents in constitutional interpretation (2010 World Congress in Mexico City), on the use of foreign law in constitution-making and amending endeavors (2014 World Congress in Oslo, Norway), explored the role played by foreign legal sources in post-conflict and in-conflict conditions (2018 World Congress in Seoul, South Korea) and went back to the original topic at the 2022 Johannesburg World Congress, by organizing a workshop on “Ten Years Later: The Use of Foreign Precedents by Constitutional”.

 

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, employing both quantitative and qualitative indicators – to what extent foreign case law is cited and the reliability of the studies describing and reporting instances of “transjudicial dialogue” between Courts.  Some of the contributions were published in T. Groppi, M.-C. Ponthoreau, The Use of Foreign Precedents by Constitutional Judges, Hart Publishing, 2013.

 

A new research project aimed at updating and completing the previous research was launched in 2021. The Group considered that in the last decade the use of foreign precedents by constitutional judges became an even more central argument in constitutional reasoning, in parallel with the growing impact of the ICT on the judicial activity and with the rise of “abusive comparative law”. As a consequence, the book Judicial Bricolage. The Use of Foreign Precedents by Constitutional Judges in the 21st century was published in 2025 by Hart Publishing, covering 31 jurisdictions.

 

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 employing both centralized and decentralized systems of judicial review.