On May 17, 2016, the Supreme Judicial Court of Massachusetts, in Isabel Kain & Others v. Department of Environmental Protection, held that the various existing greenhouse gas rules and initiatives promulgated by the Commonwealth of Massachusetts Department of Environmental Protection (DEP) did not satisfy the strict requirements of the state’s Global Warming Solutions Act. The purpose of the Act “is to attain actual, measurable, and permanent emissions reductions in the Commonwealth.” According to the Court, the unambiguous language of Section 3 (d) of the Act “requires the department to promulgate regulations that establish volumetric limits on multiple greenhouse gas emissions sources, expressed in carbon dioxide equivalents, and that such limits must decline on an annual basis.” DEP’s duty under the law was described by DEP as being mostly aspirational, but the Court held this was insufficient.

After DEP failed to take any action to implement the new law by November 2012, a group of Massachusetts residents submitted a petition for rulemaking to DEP, to which it responded by noting a number of regulatory initiatives it had taken to address global warming, but were not, admittedly, rules specifically implementing the Act. In August 2104, a complaint was filed in the Superior Court seeking declaratory relief or a writ of mandamus to compel DEP to promulgate the rules required by the Act. The Superior Court ruled for DEP, and an appeal followed. The Supreme Judicial Court ruled that DEP must issue rules pursuant to the Act that “set actual limits for sources or categories of sources that emit greenhouse gases.” By providing declaratory relief, it was not necessary to issue a writ of mandamus. By law, the rules were to take effect on January 1, 2013, and to expire on December 31, 2020.

The Act, enacted in 2008, is largely based on the California’s Global Warming Solutions Act, which was passed in 2006.