The stay was challenged by multiple states and coal industry companies, seeking to question the EPA's ability to regulate existing power plants under 7411(d) as proposed in the CPP.

As part of the amended Clean Air Act (CAA), under § 7411(d) (or Section 111 in the proposed bill), Congress granted the Environmental Protection Agency (EPA) authority to identify the "best system of emission reduction" from power generating plants or other large stationary sources, and work with states to complete implementation plans to incorporate those systems.

[2] Massachusetts v. EPA was considered one of the most significant cases in environmental litigation, as it allowed for a range of further lawsuits aimed to force emission-producing entities to limit their emissions.

[5][6] In June 2014, the United States Environmental Protection Agency (EPA) proposed The Clean Power Plan (CPP) as an Obama administration rule.

The rules aimed to tackle climate change by requiring reductions of carbon dioxide emissions from electricity generation by 32% of recorded 2005 levels by 2030, with the implementation to be set by the states, under the authority granted by the Clean Air Act, § 7411(d).

[8] This was part of the United States' commitment towards the Paris Agreement, using amendments introduced in 1990 to the Clean Air Act that identified carbon dioxide as a pollutant.

While the order was unsigned, Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan stated they would have denied the request.

[13] After the 2016 presidential election and the installation of the Trump administration at the start of 2017, the EPA effectively stated its intent to repeal the Clean Power Plan by March 2017 and to replace it with a new rule that was intended to keep its authority "within the fenceline", and asked the D.C. District to put the case in abeyance.

Proponents of the CPP urged the District court to press ahead with ruling from the September 2016, since any delay would allow the EPA to avoid its duty to uphold the Clean Air Act.

Circuit court refusal to grant further abeyance delays, the EPA issued a new proposed set of emissions regulations, the Affordable Clean Energy (ACE) rule, in August 2018.

Further, ACE kept the EPA's regulations to only steps "within the fenceline" of a power plant through emissions controls and lacked any allowance towards efficiency improvements or renewable sources.

[18][8] EPA analysis estimated this rule would increase particulate pollution compared to what was proposed under CPP, potentially leading to 1,500–3,600 more premature deaths per year by 2030 and up to 15,000 more new cases of upper respiratory problems, among other human health impacts.

The EPA argued that these initial rules were based on a limited interpretation of § 7411(d), and that other aspects of the Clean Air Act can be used to address other pollutants to reduce these numbers.

Circuit ruled 2–1 on January 19, 2021, by happenstance the day before the inauguration of Joe Biden as the next U.S. president, in favor of the plaintiffs, vacating the ACE and its repeal of the CPP.

The majority opinion ruled that the EPA's ACE rulemaking was made in an arbitrary and capricious manner intended "to slow the process for reduction of emissions", and that its implementation "hinged on a fundamental misconstruction" of the Clean Air Act's § 7411(d).

Circuit court, the EPA "can set standards on a regional or even national level, forcing dramatic changes in how and where electricity is produced, as well as transforming any other sector of the economy where stationary sources emit greenhouse gases.

"[26] In line with the findings from Michigan v. EPA, the petitioning parties expressed concern that under this interpretation of § 7411(d) "will impose costs we can never recoup because E.P.A., the state, and others will be forced to sink even more years and resources into an enterprise that is — at best — legally uncertain.

[31] Finding that the proposed action of the CPP fell under its major questions doctrine, the Court decided that it required more specific Congressional approval to be implemented.

Roberts wrote that "certain extraordinary cases, both separation of powers principles and a practical understanding of legislative intent make us 'reluctant to read into ambiguous statutory text' the delegation claimed to be lurking there... To convince us otherwise, something more than a merely plausible textual basis for the agency action is necessary.

Gorsuch wrote of the importance of the major questions doctrine, stating that it "seeks to protect against 'unintentional, oblique, or otherwise unlikely' intrusions" on the areas of "self-government, equality, fair notice, federalism, and the separation of powers".

Yet the Court today prevents congressionally authorized agency action to curb power plants’ carbon dioxide emissions.

[28] In November 2021, some legal analysts also believed that the Supreme Court's involvement is needed to resolve long-standing conflicts in § 7411(d) and other parts of the Clean Air Act.

The law's language addresses the major questions doctrine by explicitly granting EPA new authorities to regulate greenhouse gases.

[39] Some legal experts believe this would allow the EPA to set "outside the fence" regulations on existing power plants as to promote clean energy.