This paper examines the implications for U.S. fossil fuel production and global CO2 emissions of ceasing to issue new federal leases for fossil fuel extraction and not renewing existing leases for resources that are not yet producing. Avoiding dangerous climate change will require a rapid transition away from fossil fuels. By some estimates, a phase out of global fossil fuel consumption and production – particularly coal and oil – will need to be nearly complete within 50 years. Given the scale of such a transition, nations may need to consider a broad suite of policy approaches that aim not only to reduce fossil fuel demand – the current focus – but also constrain fossil fuel supply growth. This paper examines the potential emissions implications of a supply-side measure under consideration in the U.S.: ceasing to issue new leases for fossil fuel extraction on federal lands and waters, and avoiding renewals of existing leases for resources that are not yet producing. The analysis finds that under such a policy, U.S. coal production would steadily decline, moving closer to a pathway consistent with a global 2°C temperature limit. Oil and gas extraction would drop as well, but more gradually, as federal lands and waters represent a smaller fraction of national production, and these resources take longer to develop.