Institutions tend to be stable for extended periods of time, punctuated by exogenous events that can lead to institutional change. If institutions tend to reinforce their own rules and routines, it can be said that institutions cannot then change themselves. While wars and other major exogenous events can lead to institutional change, ideas are also powerful, and relatively peaceful, drivers of change. Since the establishment of an international trade regime at the Bretton Woods Conference in 1944, new ideas about the best way to organise the economy have influenced global trade, resulting in the establishment of the World Trade Organisation in 1995. The idea of free market economics led to a new global trading system, coinciding with the end of the Soviet Union, and this system has remained relatively stable since the end of Keynesianism on a global scale. Recently, however, the rise in populism and the re-emergence of nationalism have challenged the existing world order. This chapter examines the impact of the rise in populism and the re-emergence of nationalism on the international institutions of global trade. Using theories of institutional change, the chapter examines the extent to which populist ideas about free trade versus protectionism are leading to a new world economic order.