This book puts forward interlegal reasoning as a means of coping with normative legal pluralism, that is, with conflicts between competing legal systems, such as national law, European law, international law, and indigenous law. It introduces interlegal reasoning as a distinct conceptual category, bringing together interlegality and legal argumentation theory to address transnational challenges and conflicts of norms sourced in more than one legal system. In this regard, it builds upon recent literature on interlegality and legal entanglements. 
The book explicitly focuses upon legal reasoning and methodologies, especially concerning balancing. In addition to interlegality, the content is positioned in what may be described as a turn to interfaces, denoting interactive, multi-perspectival, and variable connections whose origination depends on the legalities involved, or more specifically on the legal reasoning employed by their participants concerning the facts at issue. Further, the respective contributions, in addition to focusing on legal reasoning and balancing as a method of rational justification, consider a broader scope concerning interlegal conflicts of all kinds, not merely national and international legalities. Accordingly, the book offers a valuable resource for researchers, but also practitioners, dealing with problems of intersecting and conflicting legalities.

Dr. Gabriel Alejandro Encinas Duarte, PhD, Professor at Universidad Autónoma de Baja California (Ensenada, Mexico). Alexander von Humboldt Research Fellow at the University of Erlangen-Nürnberg 2023-25. PhD in Human Rights and Global Politics, Sant’Anna School of Advanced Studies, Pisa, Italy (2017-2021). LLM in Legal Theory, Goethe University Frankfurt am Main and European Academy of Legal Theory (2017). Author of Foxes and Hedgehogs on Institutional Justification through Law: A Dialogue, UABC, 2025, coeditor of Ordenamiento Jurídico: Fundamentos y Apertura, Derecho Global Editores, 2021, and diverse articles and chapters, including “Interlegal Argumentation in the UK Drill Music decision of Meta’s Oversight Board” (Journal of Argumentation in Context), “The Idea of ‘Interlegal Balancing’ in Multilevel Settings” in the collective volume Accommodating Diversity in Multilevel Legal Orders (Routledge, 2023), and “Interlegal Balancing: A Concept, Two Contexts, Some Circumstances (Rivista di filosofia del diritto). Main fields of research: legal theory, legal pluralism, legal argumentation theory.

Prof. Dr. jur. Jan-Reinard Sieckmann, Professor of Legal Theory and Philosophy of Law at the University of Erlangen-Nürnberg, studied Law and Philosophy at the University of Göttingen, First and Second Law Exam (1983, 1990), Doctorate at the University Göttingen 1988, Habilitation at the University of Kiel 1997, Professor of Public Law at the University of Bamberg 1998-2008, since 2009 at the University of Erlangen-Nürnberg, since 2016 Professor of Legal Theory and Philosophy of Law; DAAD-Professor at the University of Buenos Aires 2007-2012. Main fields of research: legal philosophy, argumentation theory, human and constitutional rights.