The view that social justice takes priority over both global justice and the demands of sub-groups faces two critics. Particularist critics ask why societies should have fundamental significance compared with other groups as far as justice is concerned. Cosmopolitan critics ask why any social unit short of humanity as a whole should have fundamental significance as far as justice is concerned. One way of trying to answer these critics is to show that members of societies have special obligations to one another. This paper considers voluntarist and liberal nationalist accounts of such special obligations. It is especially concerned with developing a strong, sympathetic case for the less familiar nationalist position. Nonetheless, in each case the best arguments against the cosmopolitan critic require important concessions to the particularist critic. This suggests that there is a general problem with defending social justice against both critics at the same time.