In 2008, the U.S. Court of Appeals for the District of Columbia Circuit vacated the Clean Air Mercury Rule, which affected the U.S. EPA’s ability to curtail mercury emissions from coal-fired power plants. While the Obama Administration and federal courts address the issue of mercury emissions, many states have laws that are stricter than EPA’s limits. In this issue’s Feature, two researchers from the University of Colorado Boulder overview the history of these rules and present a clearer picture of how U.S. jurisdictions are addressing the mercury released from burning coal to generate electricity.