In the case of Massachusetts v. Environmental Protection Agency (EPA), several states, cities and environmental organizations petitioned for a review of the EPA's decision not to regulate greenhouse gas emissions from new motor vehicles under the Clean Air Act. The Supreme Court ruled in favor of Massachusetts et al., stating that they had standing to sue because climate change caused by these emissions could result in harm or destruction to their land. Furthermore, it was determined that carbon dioxide and other greenhouse gases are indeed air pollutants as defined within the Clean Air Act, thus falling under EPA’s regulatory authority. Therefore, the court held that unless there were scientific reasons not to do so, then EPA must set emission standards for motor vehicles.

In the dissenting opinion for Massachusetts v. Environmental Protection Agency, Chief Justice Roberts and Justices Scalia, Thomas, and Alito argued that the petitioners lacked standing to sue because they failed to demonstrate a concrete injury directly caused by EPA's inaction on greenhouse gas emissions. They contended that any harm from global warming was speculative and not traceable to EPA's refusal to regulate new vehicle emissions under the Clean Air Act. Furthermore, they questioned whether forcing EPA regulation would redress such injuries given global nature of climate change problem with many contributing factors beyond U.S vehicles' emissions. The dissent also criticized majority’s interpretation of Clean Air Act as overly broad; it suggested that if Congress intended for carbon dioxide (a ubiquitous substance) be regulated as an air pollutant due its impact on public health or welfare through climate change effects, it would have been explicit about this in legislation rather than leaving such significant policy decision up to regulatory agencies’ discretion.