The confirmation of Amy Coney Barrett to the U.S. Supreme Court would produce a 6-3 conservative majority that could have far-reaching implications for federal energy and climate policy, according to several legal experts.

Barrett, 48, did not establish a significant environmental track record from her current seat on the U.S. Court of Appeals for the 7th Circuit before being nominated Sept. 26 to fill the open Supreme Court seat created by the recent death of Justice Ruth Bader Ginsburg.

As a former law clerk for the late Justice Antonin Scalia, however, Barrett adopted the conservative icon's strict reading of the U.S. Constitution known as originalism and advanced by the Federalist Society, a group dedicated to confirming originalist judges.

Several legal experts said that view of the law, which aims to follow closely the original understandings and expectations of the Constitution’s drafters and ratifiers, could make the conservative-tilting high court even less inclined to grant federal agencies like the U.S. Environmental Protection Agency deference in regulating planet-warming greenhouse gases. Barrett's confirmation would also give the court an ideological makeup more favorable to Trump administration rules aimed at restricting the EPA's authority and more hostile to a potential Biden administration's energy and climate agenda, the experts said.

Massachusetts v. EPA

The Supreme Court has already chipped away at the EPA's authority to regulate carbon pollution through an endangerment finding issued under the Clean Air Act following its landmark Massachusetts v. EPA decision in 2007. In 2014, for example, the court in UARG v. EPA upheld the EPA's authority to require greenhouse gas controls for large emitters but found the agency exceeded its authority by attempting to require permits for thousands of smaller stationary sources.

And with the retirement in 2018 of Justice Anthony Kennedy and the addition of his replacement, Justice Brett Kavanaugh, the court no longer has the same majority that produced the 5-4 decision in Massachusetts.

"You could leave Massachusetts v. EPA untouched, but you could drain it of its efficacy by interpreting away the other authorities within the Clean Air Act to address CO2 in any kind of meaningful way," said Joe Goffman, former general counsel in the Obama EPA's Office of Air and Radiation.

Goffman said the addition of another conservative justice to the Supreme Court could have major consequences if it eventually decides Clean Air Act legal challenges dealing with the EPA's authority to regulate methane from oil and gas facilities and California's long-held waiver authority to set its own tailpipe pollution standards.

"In both cases, they overturned years and decades of the agency's own precedents," Goffman said in an interview. "That means that to the extent it is potentially a jump ball as to what the courts are going to do, you really need to have as many judges that, let's say signed up for the Federalist Society worldview, on the bench in order to increase your chances of winning what could otherwise be a tough challenge."

Nevertheless, William Yeatman, a research fellow at the libertarian-leaning Cato Institute, argued that the EPA's endangerment finding under Massachusetts should be safe even with a new conservative 6-3 majority. "No administration is going to try to remove or rescind the endangerment finding," he said. "It would be a huge political lift."

Chevron deference, nondelegation doctrine

Setting Massachusetts aside, other legal experts noted that Barrett's confirmation could lead to disputes over how the Supreme Court applies what is known as Chevron deference. Established in 1984 in Chevron v. NRDC, the precedent holds that a court may not substitute its own reading of a statute when an agency has acted on its own reasonable interpretation and Congress has not spoken clearly on the matter. Scalia originally came to be viewed as a champion of Chevron deference but expressed skepticism with its use in his later years.

The Supreme Court's five conservative justices — Clarence Thomas, Samuel Alito, Neil Gorsuch, Kavanaugh and Chief Justice John Roberts — have also indicated at times that they may be open to reviving the nondelegation doctrine in some way, noted Richard Revesz the director of the Institute for Policy Integrity at the New York University School of Law. That seldom-used legal theory holds that Congress cannot delegate its powers to administrative agencies.

"I do worry a fair amount about what a new justice might do in connection with the nondelegation doctrine and the impact that might have not only on regulation in [energy and climate] but on regulation across a whole slew of federal regulatory programs," Revesz said.

Environmental law often drives the application of these types of doctrines because so many environmental rules get challenged in court, noted Nathan Richardson, an assistant law professor at the University of South Carolina School of Law and visiting fellow at the Resources for the Future. "Chevron is the battle and nondelegation is the war," Richardson said. "It's a real dagger into the heart of the administrative state."

Regardless of the outcome of the presidential election, the confirmation of a sixth conservative justice to the Supreme Court will likely dissuade the next administration from relying on a muscular exercise of administrative authority, said Misha Tseytlin, a partner at Troutman Pepper and the former solicitor general of Wisconsin.

"If you're not going to go through regulation, you're going to go through legislation, which is preferred," Tseytlin said. "That legislation should spell out the policies that the administration wants. It should not purport to leave broad authority for the agency to decide fundamental issues of regulation because the Supreme Court, even before Justice Ginsburg's tragic death, had been suggesting that it was going to scale back broad delegations of congressional authority to agencies."