Mining companies are rhetorically committed to corporate social responsibility standards such as human rights, but what really affects their behaviour in the developing world? Communities impacted by mines have become increasingly resistant to them, bolstered and supported by international actors and norms as well as stronger domestic environmental and justice institutions. In this paper, I examine the behaviour of multinational mining companies (primarily Canadian) in two Latin American countries in the face of social resistance, finding that domestic institutional capacity and legal mobilization have an important effect on company decisions and actions. Both are necessary—the legal opportunity structure creates an institutional context in which legal mobilization is encouraged or discouraged. Litigators interacting with competent institutions have a far greater ability to hold firms to account. Thus, company practices adjust to the country’s institutional and legal context, and behaviour varies according to host country conditions.