In 2000, International Organization published a special issue on the theme of ‘legalization in world politics’ which laid the foundation for a very influential research programme on international cooperation and the role of institutions in international affairs. The most enduring legacy of the special issue is the operationalization of the concept of ‘legalization’ itself, which is defined as a combination of three dimensions: obligation, precision and delegation. After deconstructing the initial concept, this research presents a systematic evaluation of the concept of legalization, taking stock of a decade-long history of empirical use. It then proposes a new concept structure by questioning the levels of substitutability and independence originally assigned to each of the three initial dimensions.