AbstractWhen rapid economic growth catapults a country within a few years from the margins of the global economy to middle power status, does global regulatory governance need to brace for a challenge to the status quo? To answer this question, we extend the power transition theory of global economic governance to middle powers: A rising middle power should be expected to challenge the international regulatory status quo only if increasing issue‐specific strength of its regulatory state coincides with preferences that diverge from the preferences of the established powers, which are enshrined in the status quo. We examine this argument empirically, focusing on South Korea in the realm of competition law and policy. We find that South Korea, a non‐participant in the international competition regime until the 1980s, developed in the 1990s substantial regulatory capacity and capability and thus “spoiler potential.” At the same time, however, its policy preferences converged upon the norms and practices established by the United States and the European Union, albeit with some distinct elements. Under these conditions, we expect a transition from rule‐taker to rule‐promoter. We find that South Korea has indeed in recent years begun to actively promote well‐established competition law and policy norms and practices – supplemented by its distinct elements – through technical assistance programs, as well as various bilateral channels and multilateral institutions. The findings suggest that the power transition theory of global economic governance is usefully applicable to middle powers, too.