Governments that have the capacity to carry out policies – and policies that citizens support – are a key feature of state legitimacy and policy credibility. Moreover, in the context of globalization, a dimension of state legitimacy has become the capacity to conduct public policies that respond to a demand for protection. The paper argues that the deficit in legitimacy affecting many Sub-Saharan African states is explained by the following sequence of causalities, which can generate vicious circles. The reliance of Sub-Saharan African countries on primary commodities for their exports induces the “externalization” of the policies of governments, which, in turn, simultaneously erodes their legitimacy vis-à-vis citizens and capacity to conduct specific adapted policies that could reduce this reliance on commodities. These “externalized” policies have relied on a stable conceptual framework over four decades, whatever the characteristics of countries. The paper shows that this externalization takes two major forms. A first modality stems from the dependence of African governments’ fiscal policies on international commodity and financial markets, fiscal revenues depending on volatile prices that African governments cannot influence. This modality is particularly detrimental, commodity-based export structures generating the volatility of revenues, and hence fiscal deficits and indebtedness. A second modality also stems from this dependence, i.e. financing from external agencies that is conditional to policy reform. This second modality is detrimental not only because conditional financing reduces governments’ autonomy, but because it makes governments accountable to external entities and breaks a key element of political legitimacy, i.e. taxation.< Réduire