President Biden is moving swiftly on his agenda to remake large parts of the economy by wielding the powers of the executive branch. He signed more than 30 executive orders in his first month, nearly as many as the past four presidents combined at this point in their terms.

He is about to run into a formidable obstacle: a judiciary turned increasingly skeptical of regulatory authority, and conservatives determined to tap into that skepticism.

Last week, two Donald Trump-appointed judges in Texas moved to block two different early Biden actions. On Feb. 23, one imposed a nationwide injunction against the new president’s 100-day pause on deporting migrants, writing that the Department of Homeland Security had overstepped its authority and given insufficient justification for swiftly reversing a Trump-era policy.

Two days later, another judge declared unconstitutional a pandemic eviction moratorium started by Mr. Trump and extended by Mr. Biden.

Meantime, the Western Energy Alliance, a Denver-based organization representing 200 companies, is suing to stop a Biden executive order suspending oil and gas leasing on federal lands. “We like our chances in court,” said alliance president Kathleen Sgamma. “The 230-plus judges that Trump has put in place are very significant.”

It’s too soon to know how any suits will ultimately be resolved, but they are a glimpse of a restraint on Mr. Biden’s ambitions, including curbing greenhouse-gas emissions, bolstering worker protection and reducing racial inequality.

Republicans no longer control the White House or Congress, but before ceding control, former President Trump and then-Senate Majority Leader Mitch McConnell (R., Ky.) stocked the courts with a new generation of judges adhering to a growing conservative movement dedicated to reining in what some refer to as the administrative state.

“Biden and his agencies will face legal headwinds that Obama and his agencies didn’t,” said Adam J. White, a regulatory expert at George Mason University’s Antonin Scalia Law School. “If they expect to pick up where Obama left off, they’ll be in for rough sailing.”

Because Democratic administrations tend to use regulation more than Republican ones, they are more vulnerable to this movement. But many legal scholars say the courts’ higher bar on regulation is nonpartisan. Mr. Trump’s regulatory initiatives were nixed by judges—sometimes those who were his appointees—at a much higher rate than former President Barack Obama’s, according to a tracker run by New York University School of Law’s Institute for Policy Integrity.

People advising the Biden team have discussed ways to respond. These include leaning more on nonregulatory strategies, such as subsidizing renewable energy, and working with businesses to encourage voluntary behavioral change. They cite General Motors Co.’s recent decision to phase out gasoline-powered vehicles by 2035, and a move by the oil industry’s top lobbying group to endorse setting a price on carbon emissions.

Lawyers also suggest rooting new rules as much as possible in precedents upheld by conservative courts rather than asserting broad new regulatory authority

“We’re certainly aware of the legal landscape,” said White House spokesman Mike Gwin. “Reliance on data, law, and expertise is the best way to put proposed regulatory actions on a firm legal footing.”

Federal power has been gravitating toward the president and presidential appointees for decades. That reflects the growth of the federal government itself as well as the polarization of Congress. Government initiatives enacted through legislation are generally more durable because they have attracted broader political support and are less susceptible to unfavorable court judgments. But because of political gridlock, presidents have increasingly chosen the regulatory route.

Defenders of this strategy say presidents are appropriately implementing their electoral mandate. Critics say it subverts the fundamental constitutional role of a Congress elected to pass laws.

Congress has tried and failed to enact major immigration and climate legislation in recent years. Early in Mr. Obama’s term, a bill creating an emissions-trading plan to control greenhouse gases died in the Senate after narrowly passing the House even though Democrats had big majorities in both chambers. Mr. Obama turned more to regulation.

Democrats again control both the House and Senate, but by narrow margins that make it difficult to advance Mr. Biden’s most ambitious goals. Nonfiscal measures typically require 60 votes to overcome a vote-blocking procedure known as the filibuster in the Senate, where Democrats control 50 seats.

So Mr. Biden plans to lean heavily on executive orders and on regulations by agencies his appointees lead. He and his aides have repeatedly said the rush of executive orders is just the beginning of what they call a “whole-of-government approach” to advance Democratic priorities. It encompasses two dozen departments, agencies and newly created task forces. Mr. Biden has ordered an overhaul of the regulatory process to fast-track rules tailored to his goals.

Only after his executive orders are translated into specific rules will it become clearer which are likely to end up in court. But legal experts see the seeds of disputes in Mr. Biden’s campaign agenda and early actions.

The Clean Air Act was last updated in 1990, long before legislators focused on curbing greenhouse gases. Mr. Biden’s pledge of eliminating carbon emissions by 2050 will likely require a liberal interpretation of the law, environmentalists say.

Antidiscrimination laws typically target a company’s intent. Biden aides have signaled a focus not just on intent but on results, such as minority borrowers getting fewer loans or paying more than white borrowers. That is a standard known as “disparate impact” that the Supreme Court accepted, but limited, in a 2015 ruling.

Anticipating such a blitz, business groups and conservative legal organizations are preparing court challenges. Two weeks before the inauguration, an association of 26 Republican state attorneys general launched a “Save and Defend” initiative seeking opportunities to sue the new administration. That echoed a similar effort from their Democratic counterparts against the last one.

Six Republican attorneys general wrote to Mr. Biden in late January accusing him of “following the unfortunate path of executive unilateralism” and threatening to challenge the constitutionality of many of his policies.

To succeed, they are counting on a decades-long movement by conservative scholars to remake how the courts deal with executive and regulatory authority. They aim at narrowing or overturning a 1984 Supreme Court decision involving Chevron Corp. that said courts should broadly defer to regulators when laws defining the officials’ powers are ambiguous. “Chevron deference,” conservatives say, has given unelected regulators too much discretion.

Conservatives also hope to revive a doctrine called “nondelegation,” which would limit how much power Congress can delegate to agencies. The Supreme Court used that principle in 1935 to strike down parts of Franklin D. Roosevelt’s New Deal, but hasn’t touched it since.

Five current Supreme Court justices have expressed interest in reconsidering nondelegation. In a June 2019 concurrence, Justice Samuel Alito wrote: “If a majority of this Court were willing to reconsider the approach we have taken for the past 84 years, I would support that effort.”

“Those currents suggest a pincer movement that could weaken longstanding statutes and also make new statutes vulnerable,” said Lisa Heinzerling, a former official of the Obama Environmental Protection Agency who’s now at Georgetown’s law school. “That’s a danger for the Biden agenda.”

One instrumental group is the Federalist Society, which since its 1982 founding has helped shape conservative legal scholarship. An early emphasis was recruiting judges who conservatives said would interpret the law narrowly, along the lines they advocated. In the past two decades, the focus has increased on asking judges to tame bureaucrats seen as overreaching. In 2013, the Federalist Society began holding annual “executive branch review” conferences dedicated to testing regulatory law.

In 2014, Columbia Law School professor Philip Hamburger published an influential 648-page tome called “Is Administrative Law Unlawful?” He answered the question in the affirmative. Over the next three years, the book was cited approvingly by Supreme Court Justice Clarence Thomas and then-appellate-judges Neil Gorsuch and Brett Kavanaugh, two Federalist Society members since elevated by Mr. Trump to the high court.

Mr. Hamburger in 2017 launched the New Civil Liberties Alliance, a nonprofit that sues federal, state and local governments to “protect constitutional freedoms from violations by the Administrative State,” one of a number of organizations with a similar mission.

The group backed a successful Supreme Court case declaring unconstitutional the way the Securities and Exchange Commission used in-house judges. It is supporting the legal fight against eviction moratoriums and is defending a conservative publisher accused of labor-law violations by the National Labor Relations Board.

“Administrative power was once a little animal walking by your side, which occasionally barked a little but seemed harmless,” said Mr. Hamburger. “But now it has become a huge beast that is devouring almost all of our constitutional rights.”

The courts became an important check on Mr. Obama’s agenda, especially after Democrats lost control of Congress and Mr. Obama turned to what he called his pen and phone strategy to advance priorities using executive authority.

The Supreme Court scaled back the Affordable Care Act, limited the EPA’s authority over greenhouse gases and halted implementation of his plan to cut power-plant carbon emissions. Judges restricted the independence of the Consumer Financial Protection Bureau and imposition of bank-like regulation on a big insurance company, both provisions of the Dodd-Frank finance law.

When Mr. Trump took office, he set out to amplify that tendency in the judiciary. He inherited a large number of court vacancies, thanks in part to Mr. McConnell’s blocking Obama nominations, and placed 245 judges on the federal bench, more than one-fourth of the total.

When Mr. Trump left office, seven of 13 appellate circuits had Republican-appointed majorities, up from four when he entered the White House. He filled three of nine Supreme Court seats, expanding the conservative majority bloc by one.

In selecting those jurists, Trump aides emphasized candidates with a paper trail of skepticism toward regulation. They were interviewed for their views on administrative law, a new focus even for GOP administrations, White House counsel Don McGahn told the Conservative Political Action Conference in 2018.

In remarks to Mr. Hamburger’s New Civil Liberties Alliance in 2019, Mr. McGahn recounted an early White House meeting with Steve Bannon, the White House strategist at the start of the Trump administration, where Mr. Bannon was surprised to find an abridged version of Mr. Hamburger’s book on his desk. “We have a whole box here. We hand them out,” Mr. McGahn recalled saying.

Mr. Trump found himself stymied by the courts when he also tried to push the boundaries of administrative power. The Supreme Court rejected Trump administration attempts to add a citizenship question to the census and to cancel Obama-era protections for unauthorized immigrants who came to the U.S. as children. Chief Justice John Roberts wrote both opinions.

While Republican supporters of those policies were upset with the decisions, many right-leaning scholars and advocates see in them a broader, longer-term impact.

“Some of the judicial rulings overturning Trump administration actions may also be significant in limiting Biden’s regulatory options. They create new or additional roadblocks,” said Todd F. Gaziano, an official with the Pacific Legal Foundation, a group dedicated to suing regulators.