EPA ‘developing a proposed rule due out in June that could allow states to use carbon excise taxes or fees to limit the one-third of U.S. greenhouse gas emissions that come from power plants’
http://www.env-econ.net/2014/04/taxvox-blog-archive-an-epa-sanctioned-state-based-carbon-tax-could-reduce-emissions-and-improve-state-finances.html