If confirmed to a lifetime appointment, Supreme Court nominee Brett Kavanaugh could lean on a bold legal theory to block future administrations from using the U.S. Environmental Protection Agency to regulate carbon dioxide emissions from the electric utility sector.

Following his July 9 nomination by President Donald Trump, environmental groups warned that Kavanaugh would tilt the balance of the Supreme Court if he replaces Justice Anthony Kennedy, a crucial swing vote in several cases defending the EPA's authority to issue air quality and CO2 rules.

That argument was advanced again Sept. 7 by Lisa Heinzerling, an expert witness called by Democrats on the Senate Judiciary Committee to testify on the final day of Kavanaugh's contentious confirmation hearings.

In prepared remarks, the Georgetown University law professor noted Kavanaugh has often ruled on the side of businesses seeking to overturn environmental regulations during his 12-year tenure as a judge on the U.S. Court of Appeals for the District of Columbia Circuit.

Heinzerling also told committee members that Kavanaugh has put his own twist on a legal theory known as the "major rules" doctrine, which could strip agencies of the legal authority needed to tackle issues such as climate change.

The theory "holds that an agency may not issue a rule that has great political and economic significance without a precise and crystalline instruction from Congress," Heinzerling said. "This interpretive approach would, perversely, disable agencies in the very circumstances in which we need them the most."

'Major rules' doctrine

The "major rules" doctrine stems from a 2015 Supreme Court decision in King v. Burwell, in which the court upheld tax-related provisions in the Obama administration's Affordable Care Act.

Although the case was widely viewed as a loss for conservatives, the court also articulated a "major rules" exception to a precedent known as the Chevron deference. The longstanding precedent, first established by the Supreme Court in the 1980s, holds that courts should generally defer to federal agencies' interpretations of regulations that are ambiguous or silent on a particular issue.

But in King v. Burwell, the Supreme Court's outlined a "major rules" exception by stating that courts need not defer to agencies if the regulation involves an issue of major political or economic significance.

A year later, Kavanaugh dissented from a D.C. Circuit Court denial to rehear a lawsuit brought by telecommunications companies challenging the Federal Communications Commission's net neutrality rule governing internet service providers. According to Heinzerling, Kavanaugh in a written dissent staked out a more expansive position than the Supreme Court's "major rules" exception.

"For an agency to issue a major rule, Congress must clearly authorize the agency to do so. If a statute only ambiguously supplies authority for the major rule, the rule is unlawful," wrote Kavanaugh.

Heinzerling's analysis suggests that Kavanaugh's position, if established as Supreme Court precedent, could stand in the way of future attempts by the EPA to use its broad authority under the 1970s Clean Air Act to enact a nationwide CO2 reduction plan similar to the Obama administration's Clean Power Plan.

Moreover, Heinzerling noted that Kavanaugh would distinguish "major" rules from "ordinary" rules by considering "the amount of money involved for regulated and affected parties, the overall effect on the economy, the number of people affected, and the degree of congressional and public attention to the issue."

"He has already announced that rules governing the Internet and regulating greenhouse gases are off-limits under his theory," Heinzerling said, citing Kavanaugh's dissent from a 2012 court decision upholding an EPA rule that limits greenhouse gas permitting to the largest industrial sources.

'Not a skeptic of regulation at all'

Meanwhile, Kavanaugh suggested on Sept. 5 that agencies sometimes improperly lean on legal precedent to promote environmental objectives beyond the scope of the law. It is up to Congress, not the courts, to address those issues, he argued.

"We have to stick to the laws passed by Congress," he said on the second day of his confirmation hearing. "You make the policy, we'll follow the policy direction ... we don't rewrite those laws."

Kavanaugh also said he is "not a skeptic of regulation at all."

"I'm a skeptic of unauthorized regulation, illegal regulation, regulation that's outside the bounds of what the laws passed by Congress have said," he said.

Adam White, director of the Center for the Study of the Administrative State at George Washington University, came to his defense two days later.

"In an era where agencies are often eager to enact policies that Congress hasn't legislated, some of Judge Kavanaugh's critics favor those energetic agencies over Congress," White said. "Especially in recent cases involving agencies claiming immense new regulatory powers under the guise of decades-old statutes."

White said Kavanaugh's approach represents "administrative law at its best." The approach empowers "agencies to administer the laws efficiently and effectively, but always subject to the deeper fundamental commitments of our Constitution's structure and rights," White said.

Past predicts future?

Michael Gerrard, an environmental law and energy regulation professor at Columbia Law School, said in a Sept. 11 interview that examining Kavanaugh's track record can be even more illuminating than scrutinizing his legal theories.

Kavanaugh dissented with the majority of a three-judge panel on a challenge to the EPA's Mercury and Air Toxics Standards, or MATS, in White Stallion Energy Center v. EPA (No. 12-1100). In his dissent, Kavanaugh said the notion that Congress would authorize the agency to regulate without any consideration of regulatory costs was unreasonable. The Supreme Court later ruled that the EPA did not properly consider the cost of compliance when developing MATS.

In EME Homer City Generation v. EPA (No. 11-1302), Kavanaugh was also part of a panel that vacated the EPA's Cross-State Air Pollution Rule, known as CSAPR. In that decision, he found the rule required states to make emissions reductions beyond what was legally required. The Supreme Court later reversed the D.C. Court's decision, determining that the EPA's over-control of some states did not require the entire rule to be vacated.

"A court with a solid five-judge conservative majority that includes Judge Kavanaugh is likely to be more resistant to the innovative or expansive use of existing regulatory statutes, including environmental" rules, Gerrard said. "He interprets statutory authority exceedingly narrowly."