The D.C. Circuit vacated a portion of EPA's 2013 rule regulating air emissions from Portland cement kilns. The court concluded that the emission-related portions of the rule are permissible under the CAA.

A district court held that Minnesota's New Generation Energy Act, which establishes energy and environmental standards related to carbon dioxide emissions, constitutes impermissible extraterritorial legislation and is a per se violation of the dormant Commerce Clause.

The D.C. Circuit upheld the Occupational Safety and Health Review Commission's finding that SeaWorld violated the OSH Act by exposing trainers to recognized hazards when working in close contact with killer whales during performances.

The D.C. Circuit held that the Securities and Exchange Commission's (SEC's) "conflict materials" rule violates the First Amendment.

A district court dismissed three New Hampshire cities' citizen suit challenging EPA's decision to approve New Hampshire's impaired waters list under the CWA.

The Ninth Circuit held that the Bureau of Reclamation should have consulted with FWS or NMFS on impacts to the threatened delta smelt prior to renewing long-term water contracts pertaining to California's Central Valley Project.

A district court granted summary judgment in favor of NMFS in a lawsuit filed by Massachusetts and New Hampshire challenging the agency's decision to promulgate Frameworks 48 and 50 regulating New England’s Multispecies Fishery under the Magnuson-Stevens Fishery Conservation and Management A

 The primary standards for carbon monoxide have remained the same since 1971. There has not been a secondary standard for carbon monoxide since EPA revoked a secondary standard in 1985.

The D.C. Circuit upheld the emission standards EPA promulgated in 2012 for mercury and other listed hazardous air pollutants emitted by coal- and oil-fired electric utility steam generating units.