A WTO member state whose legislation is alleged to have infringed WTO rules often invokes the mandatory/discretionary distinction, which states that only legislation mandating actions inconsistent with WTO rules can be challenged; legislation merely granting the discretion to do so cannot be challenged. This article highlights the treatment of this distinction by the Panel and the Appellate Body in recent decisions, in particular, United States–Section 211 Omnibus Appropriation Act of 1998 (‘US–Section 211’), and United States – Countervailing Measures Concerning Certain Products from the European Communities (‘US–Countervailing Measures’). The reasoning and analysis in these cases extended beyond the characterization of the form of the legislation to an examination of the effect of the legislation, and may portend a reconsideration of the mandatory/discretionary distinction and a reformulation of the test for reviewing a state's legislation for WTO-compliance.