This introduction and the contributions of this HSR Special Issue “Conventions and Law from a Historical Perspective” present the conception and analysis of law from the perspective of the French institutionalist approach of the economics of convention (EC). From the pragmatic viewpoint of EC, law is regarded as an institution through which actors “identify” the situation in which they interact regularly. Law can be seen as a “guide” in the coordinations in which actors are engaged and committed. So law is not conceived as simple external constraint for economic action because law has to be interpreted and mobilized by competent actors. Therefore, EC understands law as internal to situational coordinations. From its beginnings (three decades ago), EC has included the analysis of law into its institutional research. Also from its beginnings, EC has developed a transdisciplinary approach, refusing the traditional “division of law” between history, sociology, economics, and law science. The introduction presents some main concepts (as convention of State) and positions of EC in the analysis of law. This introduction also relates EC’s perspective to neoliberalism, economic neo-institutionalism, new historical institutionalism, and the Weberian sociology of law. The contributions of this HSR Special Issue are presented. They cover overviews about EC’s research on (mainly economic) law, empirical applications, and theoretical considerations about law from a conventionalist perspective.