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.