[JURIST] The US Court of Appeals for the District of Columbia Circuit [official website] on Thursday granted a request from the Trump administration to stay ligation concerning an Obama administration air pollution regulation. The rule in question, the Mercury and Air Toxics Standard (MATS) [EPA backgrounder], has been in place for numerous years and has many coal-fired power plants have already come into compliance with its terms. Many industry groups and 15 state prosecutors, included current EPA Administrator Scott Pruitt [official profile], challenged the rule. As a result of the court’s action, all of the pending litigation around the country has been stayed [Reuters report] in order for the EPA to review the rule.

MATS, which was enacted under the Clean Air Act (CAA) [materials, PDF], has been a controversial regulation.In March the Supreme Court ordered that the Obama administration delay enforcement [JURIST report] of the EPA’s Clean Power Plan (CPP) [materials], of which MATS is a part of, pending a resolution to legal challenges. The request to block the implementation of the CPP was made in late January 2016, with states insisting [JURIST report] that the plan’s implementation would create a burden on states. Regulating power plant emissions has been a contentious issue. In June 2016 the Supreme Court ruled [JURIST report] 5-4 that the EPA could not make regulations regarding the toxic emissions of power plants without considering costs.