This paper discusses an important legal issue raised by the United States in its recent attempt to block the reappointment of an Appellate Body member. According to the US, in some of his decisions, the member has made overreaching findings that amount to obiter dicta. As obiter dictum is a unique concept in the Common Law system, the US argument may only stand if the concept may be found in the WTO legal system as well. With a careful analysis of the concept of dicta in Common Law and a close examination of the effects of past panel and Appellate Body decisions in WTO dispute settlement, the paper rejects the US argument by refuting each of the three premises of the US argument, i.e., the WTO legal system based on Common Law; WTO follows stare decisis; and the WTO has rules against dicta. In addition to original contributions on the nature of the WTO dispute settlement system in theory, the article also provides some practical advice on how the controversy may be resolved.