The AB Report in US-Clove Cigarettes confirmed the Panel's conclusions that imported clove cigarettes were 'like' US menthol cigarettes, and accorded 'less favourable treatment' for the purpose of national treatment under Article 2.1 TBT, but it employed significantly different logic. The AB's reasoning extends earlier GATT jurisprudence into the TBT, applying competition-oriented analysis to the question of product definition, while reserving consideration of regulatory purpose to the comparison of treatment. We consider this emphasis from the perspectives of legal and economic indeterminacy, which we find run in parallel to each other. In the particular questions of the appeal, the AB's decisions are sensible from both perspectives, but ultimately do not add significantly to determinacy. We find it impossible to ignore regulatory purpose in discrimination cases, and we provide a novel economic model for analysing regulatory utility in this respect. In our view, there is not much economic difference in analysing regulatory purpose separately from more observable market considerations, but this sequencing does add political logic, analytical focus and formal transparency, all of which may enhance the legitimacy of WTO dispute settlement rulings, although ideally, further specification from the WTO Membership regarding the methodological content of the national treatment discipline would be preferred.