Judge Brett M. Kavanaugh, in cases involving federal regulation, tends to focus on whether the action has specific congressional authorization. (J. Scott Applewhite/AP)

The White House did not mince words when it introduced Judge Brett M. Kavanaugh to business and industry leaders on the occasion of his nomination to the Supreme Court this summer.

“Judge Kavanaugh has overruled federal agency action 75 times,” the administration said in a one-page unsigned memo touting what it considered the highlights of Kavanaugh’s 12 years as a judge on the U.S. Court of Appeals for the District of Columbia Circuit.

“Judge Kavanaugh protects American businesses from illegal job-killing regulation,” the memo said. “Judge Kavanaugh helped kill President Obama’s most destructive new environmental rules.”

Hot-button social issues such as abortion and race have so far dominated the debate about Kavanaugh’s nomination, but there is no more important issue to the Trump administration than bringing to heel the federal agencies and regulatory entities that, in Kavanaugh’s words, form “a headless fourth branch of the U.S. Government.”

“The ever-growing, unaccountable administrative state is a direct threat to individual liberty,” White House Counsel Donald McGahn said in a speech to the conservative Federalist Society in the fall. He has said the Trump administration’s efforts to strike down government regulations will be meaningless without judges who will “stand strong.”

As he told another conservative group, “There is a coherent plan here where actually the judicial selection and the deregulatory effort are really the flip side of the same coin.”

Kavanaugh, 53, for years has been an influential judicial voice questioning the administrative state, with a string of opinions that would sharply limit the power of federal agencies, including the Nuclear Regulatory Commission, the Labor Department’s Occupational Safety and Health Administration and the Environmental Protection Agency. The decisions concern a long list of topics — mortgage abuse, greenhouse gases, even protecting employees from killer whales.

His nomination concerns some who say the agencies’ rulemaking powers protect the public.

“This is the end of the regulatory state as we know it,” said Rena Steinzor, a University of Maryland law professor who specializes in administrative law. “If he goes up there, they will never find a regulation they find acceptable. And they’re going to be making the policy.”

Kavanaugh’s confirmation, for instance, could call into question the Supreme Court’s 5-to-4 ruling in Massachusetts v. EPA; in 2007, the court said greenhouse gases blamed for global warming could be regulated under the Clean Air Act. The justice he would replace, Anthony M. Kennedy, joined the court’s liberals to form the slim majority.

The ruling opened a new front for EPA regulation, but Kavanaugh has routinely ruled against the agency’s efforts.

“EPA’s well-intentioned policy objectives with respect to climate change do not on their own authorize the agency to regulate. The agency must have statutory authority for the regulations it wants to issue,” Kavanaugh wrote in a recent opinion about manufacturers using hydrofluorocarbons, potent greenhouse gases known as HFCs.

He added that “Congress’s failure to enact general climate change legislation does not license an agency to take matters into its own hands, even to solve a pressing policy issue such as climate change.”

Julia Stein, a UCLA law professor who specializes in environmental law, wrote in an analysis that Kavanaugh’s rulings would limit the agency’s efforts in the face of congressional gridlock.

“In a world where comprehensive climate change legislation appears to be a long way off, a Justice Kavanaugh would likely present a hurdle to future agency attempts to regulate climate change within the existing statutory framework,” she wrote.

Kavanaugh has participated in more than 300 opinions, about a third of them dealing with the scope of regulatory agencies.

The judge’s supporters say he rules for agencies when he finds they are exercising power specifically granted by Congress, but only after a thorough examination.

“Kavanaugh takes the underlying questions about the legitimacy of any agency’s actions very seriously,” said Jonathan H. Adler, director of the Center for Business Law and Regulation at the Case Western Reserve University School of Law. “His response has been to enforce the rules pretty strictly.”

His positions often take issue with the role of independent agencies — from the late 1800s in regulating railroads through the 2009 financial reforms — established with the purpose of protecting the public from more powerful individuals and corporations. Over time, these agencies often adapt to deal with new problems in their areas not specifically mentioned by Congress when they were created.

In one case, he ruled in favor of SeaWorld, which had been fined $75,000 by OSHA after a killer whale dismembered and drowned a trainer in front of hundreds of visitors. OSHA said SeaWorld knew from earlier incidents that the whale was highly dangerous.

A majority of the three-judge appeals court panel backed OSHA. But Kavanaugh dissented, calling OSHA’s action “arbitrary and capricious” because regulating the safety of killer-whale shows is no different from regulating the safety of tackling in football or speeding in auto racing or punching in boxing.

He wrote that the Labor Department “lacks authority to regulate the normal activities of participants in sports events or entertainment shows.”

In PHH v. Consumer ­Financial Protection Bureau , ­Kavanaugh’s colleagues on the circuit court overturned his decision that the agency lacked authority because its sole director was not subject to dismissal by the president.

“This is a case about executive power and individual liberty,” he wrote, siding with PHH, a mortgage lender that challenged the CFPB after it fined the company $109 million.

“Because of their massive power and the absence of Presidential supervision and direction, independent agencies pose a significant threat to individual liberty and to the constitutional system of separation of powers and checks and balances.”

The majority in the case said that “PHH makes no secret of its wholesale attack on independent agencies — whether collectively or individually led — that, if accepted, would broadly transform modern government.”

It is often in dissent that Kavanaugh has moved the law. Asked by the Senate Judiciary Committee to list his 10 most significant opinions, four of the top five were cases in which Kavanaugh disagreed with his colleagues on the D.C. Circuit but was later supported by the Supreme Court.

At the top of the list was a case in which he dissented when a panel of his court upheld the constitutionality of the Public Company Accounting Oversight Board.

“In my view,” Kavanaugh told the senators in his questionnaire, “a key feature of the board’s structure — that its members were removable only ‘for cause’ by the Securities and Exchange Commission, whose members were removable only ‘for cause’ by the President — unconstitutionally limited the President’s Article II authority to supervise the Executive Branch.”

The Supreme Court’s conservatives, in a 5-to-4 vote, agreed with Kavanaugh.

Kavanaugh also argued against the ability of agencies created in an earlier era to regulate modern business. In a case regarding net neutrality, he wrote that the Federal Communications Commission lacked the authority to regulate without explicit instructions from Congress.

“Congress has debated net neutrality for many years, but Congress has never enacted net neutrality legislation or clearly authorized the FCC to impose common-carrier obligations on Internet service providers,” Kavanaugh wrote. “The lack of clear congressional authorization matters.”

Kavanaugh is especially concerned with the “major rules doctrine.” Congressional authorization would be needed for any regulation of vast economic or political significance — a major rule.

Ian Fein, a lawyer with the Natural Resources Defense Council, said the doctrine would “turn parts of administrative law on its head and strip agencies of power they currently have under numerous statutes to deal with problems that arise in different areas.”

Fein said: “Congress passes laws that establish agencies that deal with new problems that arise. Under Kavanaugh, agencies would not be able to use existing power. They would have to go to Congress to enact new laws.”

Kavanaugh’s opinions have drawn opposition from groups not normally outspoken on judicial appointments. The NRDC has announced that it opposes Kavanaugh’s nomination; its only prior public opposition to a Supreme Court nominee was to Justice Samuel A. Alito Jr.

Other environmentalist groups are also alarmed. They point to a case called EME Homer City Generation, L.P. v. EPA. Kavanaugh wrote a majority opinion saying that the EPA could not regulate pollution from one state that was afflicting other states downwind — even if the state spewing emissions was harming the health of those downwind.

“It undercuts environmental protection to such an extent that it hearkens back to pre-EPA powers when we had tragedies like Love Canal and 1969 burning of the Cuyahoga River,” said Pat Gallagher, director of the environmental law program at the Sierra Club. “Kavanaugh’s speeches, opinions and writings all indicate antipathy toward strong regulatory powers like EPA needs to do its job.”

It is also the one instance in which the Supreme Court reversed a Kavanaugh decision, ruling 6 to 2 for the EPA.

Another reason Kavanaugh has upset environmentalists: In some cases, he made it tougher for independent groups such as the NRDC to file suits to protect the public interest and health. In Public Citizen, Inc. v. National Highway Traffic Safety Administration, Kavanaugh’s 2007 majority ruling questioned Public Citizen’s standing based on increased risk of future harm.

“Kavanaugh questioned whether the courthouse door should ever be opened to plaintiffs suing based on increased risk of harm created by the action they’re challenging,” Fein, the NRDC lawyer, said in an interview. “That would have a dramatic impact on citizens but also organizations like NRDC that bring lawsuits to try to protect the public health and welfare. It is deeply troubling.”

Adler said his review of Kavanaugh’s decisions shows him to be “evenhanded,” using the same evaluation of agency actions whether they could be characterized as liberal or conservative.

The judge in some cases has upheld EPA regulations and in at least one case found that environmental groups had the legal standing to intervene in a case, Adler said.

Others, such as Washington lawyer Eric Citron, who analyzed Kavanaugh’s record for Scotusblog.com, found the judge to be a “reflexive” friend of business.

“Those who worry that Kavanaugh’s judicial philosophy will stand as a barrier to government regulation of big businesses — including when it comes to policies like net neutrality — are right to feel that way,” he wrote. “Conversely, those who celebrate that philosophy as tending to make the market and the country a freer place will find a like-minded champion on the Supreme Court.”

Seung Min Kim contributed to this report.