Taking into account uncertainties in the governance of a liberal economic reform leads to a challenging paradox. Economic reform requires institutional stability, which is guaranteed by the independence of the economic regulation authorities from political influence and by a loyalty to initial institutional commitments and international standards. However, all economic reform includes a degree of uncertainty in its results. This uncertainty can be reduced during the implementation of the reform. Experience may lead national governments or independent regulatory authorities to introduce adjustments. Nevertheless, adjustments are limited by the initial institutional commitments and institutionalized standards. The case of the liberalization of the electricity sector in France illustrates this paradox. By articulating the sociology of science and technology to new institutionalist theory in sociology, this communication develops the concept of “flexible institution” in order to explain how a highly institutionalized economic model, the electricity market, has been adapted to the political and material specificities of the French energy system.