The last time the Supreme Court heard a major case about climate change, the judges split along ideological lines and ultimately favored the argument that the Clean Air Act gave the Environmental Protection Agency (EPA) the authority to regulate carbon emissions. The decision in Massachusetts v EPA set the stage for the current battle on Capitol Hill that now sees Republicans fighting to rein in the EPA’s extended power to regulate.

On Tuesday, the Court will once again hear a major environmental case that has the potential to actually create policy through the judiciary branch on the subject of climate change. This time, however, some observers are optimistic the justices will leave the policy-making to the legislative and executive branches.

In American Electric Power v Connecticut, six states and one city (Connecticut, Iowa, California, New York, Rhode Island, Vermont and New York City) are arguing that common public nuisance laws give them the power to sue power companies to reduce emissions that cause global warming.

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