This article considers the resistance potential of Environmental Impact Assessments (EIAs) and their effects upon existing power relationships. It focuses upon the blocking of Eskom’s proposed new test nuclear reactor by the environmental NGO Earthlife Africa, at Koeberg, South Africa, the site of Africa’s only existing nuclear power plant. This was achieved through their engagement with, and contestation of, the South African EIA process. It occurred within a context of a globally uncertain future for the nuclear industry, and broader questions over the possible role of nuclear power in sustainable development. Whilst initially appearing as an example of environmental resistance against a big development project, by approaching the case through the lens of Michel Foucault’s concept of governmentality the article suggests that Earthlife Africa’s challenge reinforced existing power relationships and legitimised an essentially pro-development EIA process. This is particularly evident when considering the relationship between EIAs and established scientific authorities, and the problematic role of public participation. However, by regarding the EIA as an example of ‘bearing witness’ some sense of its resistance potential can be reclaimed. The article concludes by suggesting that a broader debate on nuclear power in South Africa is desirable, and that environmental NGOs should seriously consider the degree to which they accept and participate in the EIA process.