In both the United States and France, each side of the legal battle over same-sex marriage and parenthood relied heavily on experts. Despite the similarity of issues, however, lawmakers in each country turned to different sets of authorities: from economists and psychoanalysts to priests and ordinary people. They even prized different types of expertise—empirical research in the United States versus abstract theory in France.

Exploring the legalization of same-sex marriage in the United States and France, this book sheds new light on the power of experts to influence high-stakes democratic debates. Drawing on extensive interviews and ethnographic observation, Michael Stambolis-Ruhstorfer traces the divergences between the two countries, showing why some experts are ubiquitous in one but absent in the other. He argues that lawmakers, judges, lawyers, journalists, and activists covet something only experts can provide: the credibility and aura of authority, or “expert capital,” which they deploy to advance their agendas. Expert capital is not derived from scientific or technical merit alone but is produced through cultural norms, material resources, and social relationships, which vary greatly across national contexts.

Through the story of the fight over gay rights, By the Power Vested in Me reveals how and why certain experts—but not others—obtain the authority to shape public opinion and policy. At a time of soaring public distrust in experts, this book offers new ways to understand the contested political role of expertise and its consequences.

Michael Stambolis-Ruhstorfer is a sociologist and associate professor of American studies at the University of Toulouse–Jean Jaurès and junior member of the Institut Universitaire de France.