Abstract There has been a recent rise in very large-scale transnational commercial land acquisitions in the global South—notably in sub-Saharan Africa. Such acquisitions, often referred to as land grabs, accelerated sharply after the 2007–8 world food crisis. The issue of land grabs intersects with issues of climate change. Many climate change mitigation efforts—most notably the turn to biofuels—generate a huge demand for land that is then satisfied by land grabs. Land grabs themselves undermine climate change mitigation initiatives as massive commercial agriculture is associated with deforestation as well as a turn towards monoculture, a land use option that generates extensive emissions. With a focus on countries in sub-Saharan Africa, this article considers the possibilities of using customary/traditional law and tenure systems to limit land grabs and mitigate their negative environmental impacts, including impacts on climate. Many of the countries that are targets in the global land rush are postcolonial countries that feature plural legal systems. They have a formal legal system, usually one introduced as part of the colonial enterprise, that is based on a Western civil law or common law system. They also feature a customary legal system that is often subordinate to the formal legal system, though it tends to be in widespread use in some parts of the country, particularly in rural areas. This legal system entails a separate governance framework as well as a customary land tenure regime. Customary land uses tend to have minimal negative impacts on local communities and on the environment relative to the land uses associated with transnational land transactions. Customary legal systems can also be used to resist large-scale land acquisitions and mitigate their negative social and environmental impacts. Two channels by which this can occur are addressed. First is the idea that customary law governance frameworks create a governance counterpoint to central government and so a local institutional framework that facilitates some resistance to power from the political centre. This framework can facilitate resistance to some deleterious land transactions. Second is the notion that customary land tenure systems generally embody a different idea of property, an idea that is relatively communitarian. This idea can be engrafted onto property as understood within the country’s legal system so as to protect some access to essential resources for local communities, even in the wake of large-scale land transactions. More broadly, this conception of property—including its tendencies against private alienation—can also be deployed to exclude some transnational land transactions altogether.