Abstract: In the Commonwealth nations, a constitutional “convention” denotes an unwritten but obligatory constitutional custom or norm. The question I will address is whether public law in the United States should be understood to permit, require or forbid federal courts to incorporate conventions into their decisions. My major claim is that public law should adopt an approach that has achieved consensus status in the United Kingdom and Commonwealth – what I will call the “modern Commonwealth view.” This approach holds that while courts may and should recognize conventions, they may not and should not enforce them. The main strength of the modern Commonwealth view is that it is not either of two other leading views, which I will call the “classical Diceyan view” and the “incorporationist view” respectively. I will argue that the two competing views are untenable and undesirable, and that the modern Commonwealth view triumphs faute de mieux – for lack of a better, or even any feasible, alternative. Moreover, I will claim that in important cases, especially recent cases, the U.S. Supreme Court has implicitly moved toward just this approach.