This paper explores how the use administrative discretion is affected by courts and tribunals having the power to interpret international treaties. In particular, the paper examines the impact of a distinct part of the practice of three different courts and tribunals: (1) The WTO Appellate Body and its interpretation of the World Trade Organization Agreement on the Application of Sanitary and Phytosanitary Measures; (2) the practice of arbitration tribunals which having the power to interpret bilateral investment treaties (BITs); and (3) the Court of Justice of the European Union’s interpretation of the Treaty on the Functioning of the European Union and its prohibitions against restrictions on free movement. The paper demonstrates how the practice of these courts and tribunals imposes limitations on the use of administrative discretion which affects substantial portions of administrative activity in modern states, namely, the regulation of risk, property, and the movement of goods, persons, services and capital. On this basis, the paper argues that it is imperative that the future doctrine of administrative law take the practice of international courts and tribunals into account in its examinations and presentations of the norms determining the discretionary powers of administrative authorities.