[5] Before entering academia, Shaffer was a member of the Paris bar, working at the law firms of Coudert Frères and Bredin Prat.

Shaffer is a leading international trade expert, author, and consultant on the World Trade Organization (WTO), European Union law, globalization, transnational legal orders, and transnational legal ordering.

[8] He introduced the concepts of public-private partnerships and legal capacity in the WTO dispute settlement system, examining how they work in practice in the United States, the European Union, Brazil, India, and China.

[9] Shaffer has written major books on the international law and politics governing genetically modified foods, transatlantic relations, and works in the tradition of legal realism and socio-legal studies.

[10] His publications include nine books and over 100 articles and book chapters, including, Emerging Powers and the World Trading System: The Past and Future of International Economic Law (2021), Constitution-Making and Transnational Legal Order (Ginsburg and Halliday, 2019), Transnational Legal Orders (Halliday, 2015), and Transnational Legal Ordering and State Change (2013).