This article evaluates the theory of boundary legitimacy put forward in A. J. Simmons’ recent book Boundaries of Authority. I believe Simmons is correct to hold that questions about the legitimacy of political boundaries are distinct from questions about the justice of political institutions. But I argue that Simmons’ own theory makes legitimate boundaries depend far too strongly on historical processes in the past, with implausible implications. I conclude with some thoughts about how a broadly Kantian theory might take on board the most important insights of Simmons’ work.
