In its last published opinion of the term, the United States Supreme Court held that EPA should not have ignored costs in deciding whether to regulate mercury and other hazardous air emissions from coal- and oil-fired power plants.  In that regulation, known as EPA’s Mercury and Air Toxics Standards (MATS), EPA had attempted to demonstrate that such regulation was “appropriate and necessary” without considering cost.  Although four justices found EPA’s actions to be reasonable based on the theory that EPA considered costs later in the process of setting specific emission limits, a five-justice majority held that EPA had acted unreasonably in ignoring costs in its threshold “appropriate and necessary” finding.

On June 12, EPA published its final SSM SIP Call recalling EPA-approved state air rules governing emissions associated with startup, shutdown and malfunction events at regulated facilities in 36 states.  The list of affected states is posted on EPA’s website here.  Some of these state rules have been approved and on the books for decades, while others were approved by EPA just within the last several years.  EPA is giving the affected states until November 22, 2016 to revise their SIPs and submit any new provisions to EPA for review and approval.