The primary focus of this paper is to examine the link between environmental R&D formation and the strategic use or non‐use of a government's ability to precommit to an emissions tax rate. The existing literature implicitly omits this important matter. This paper comprehensively evaluates various regulatory contexts separated by the timing of emissions taxation and by environmental R&D formations in a Cournot duopoly. The following three points are revealed. First, an equilibrium occurs in which the government does not strategically use its emissions tax rate precommitment ability to enhance social efficiency. Second, if the efficiency of environmental R&D costs is high and if environmental damage is serious, then the government should precommit to an emissions tax rate and allow for the cartelization of the two firms' environmental R&D. However, if the environmental R&D cost efficiency and environmental damage are both low, then the government should adopt a time‐consistent emissions tax and allow for the cartelization of the two firms' environmental R&D. Third, when the two firms can form an environmental research joint venture (ERJV), ERJV cartelization should be invariably allowed, even if the government is a strategic non‐user of its precommitment ability.