We review the WTO Appellate Body report on United States – Sunset Reviews of Anti-Dumping Measures on Oil Country Tubular Goods from Argentina (WT/DS268/AB/R, 29 November 2004). This dispute is one of several that deals with sunset reviews of antidumping-duty orders. In its ruling, the AB reasserts a rigid distinction between mandatory and discretionary law, and sets a very high standard for Member challenges to laws or practices that allow for violations of WTO obligations but do not mandate such behavior. We argue that this ruling is unfortunate, because it diminishes scope of and incentives for ‘as-such’ challenges to laws and practices, which have a potentially useful role to play in the world trading system. The AB ruling also overlooks the purpose and objectives of sunset reviews – to ensure that duty orders are not extended when their removal would generate no harm to an import competing industry – by failing to impose sufficient discipline on their conduct. We argue that a sunset review requires an evaluation of competitive conditions in the industry and of the reasons and incentives for dumping, in order that the investigating authority can judge whether the removal of a duty order would lead to a continuation or recurrence of dumping and injury. The Appellate Body's rulings in this and other similar cases have the effect of relieving the investigating authority of this responsibility and thereby render the sunset review process virtually meaningless.