Many political philosophers who embrace some version of a Lockean-based theory of justice have accepted Locke's Proviso concerning the duty of appropriators of natural resources to leave enough and as good for others. I argue that if the Lockean Proviso should be applied to the appropriation of natural resources, then it should also be applied (extended) to the use of unappropriated natural resources. To demonstrate the plausibility of applying the Lockean Proviso to use of unappropriated natural resources, I consider cases where agents engage in the destructive use, degrading use, overuse and restricting access use of unappropriated natural resources. After considering these cases of morally problematic use, I maintain that the removal of a natural resource (either by means of appropriation or use) is the relevant moral feature that triggers the duty to leave enough and as good for others. While considering the implications of extending the Lockean Proviso to encompass cases of using unappropriated natural resources, the article also explores the impacts of this finding directed toward an understanding of the ‘tragedy of the commons’. The extension of the Lockean Proviso to encompass the use of unappropriated natural resources has widespread general implications for any Lockean-based theory of justice.