In recent years, scholars argue that, although the principle of fair play is able to establish obligations to reciprocate for benefits received, these do not include political obligations. They contend that recipients themselves should be able to determine the form their recompense takes. I examine different cases of benefit provision and identify instances in which the principle of fair play does not allow such discretion. An important consideration is epistemic difficulties that can be avoided only if citizens accept the judgment of law and follow it. In familiar political obligation cases, disagreements about benefits and burdens should be resolved by democratic procedures. Following decisions arrived at is necessary to avoid problems of two kinds: moral, making sure burdens of cooperation are distributed in ways that are fair to all participants; and empirical/sociological, making sure important benefits are provided.