Interpreters of Robert Nozick’s political philosophy fall into two broad groups concerning his application of the ‘Lockean proviso’. Some read his argument in an undemanding way: individual instances of ownership which make people worse off than they would have been in a world without any ownership are unjust. Others read the argument in a demanding way: individual instances of ownership which make people worse off than they would have been in a world without that particular ownership are unjust. While I argue that the former reading is correct as an interpretive matter, I suggest that this reading is nonetheless highly demanding. In particular, I argue that it is demanding when it is expanded to include the protection of nonhuman animals; if such beings are right bearers, as more and more academics are beginning to suggest, then there is no nonarbitrary reason to exclude them from the protection of the proviso.