Companies are bracing for the fallout of a decision by the Supreme Court last week that allows the president to fire members of federal regulatory boards for any reason, stripping those regulators of their independence from the White House.

The decision has implications for more than a dozen agencies that oversee power companies, railways, investment banks, labor disputes and the biggest technology companies. Now, corporate executives and lawyers are grappling with the potential for these agencies — which set the rules and enforce them — to become even more political.

The decision “enables a lot more mischief,” said Douglas Melamed, a former general counsel at the chip maker Intel and a former senior official at the Justice Department. “The president is totally free to micromanage things and really squeeze these agencies.”

The ruling adds to the unpredictability of doing business in the United States, where regulation has heavily depended on which party is in power. Republicans tended to loosen the rules, while Democrats tended to add restrictions.

Under the Biden administration, for example, regulators limited drilling on public lands, banned noncompete agreements and sued Adobe and Live Nation, arguing that the companies broke antitrust and consumer protection laws. After President Trump took office a second time, his appointees quickly reversed or abandoned those decisions and settled those lawsuits.

These policy swings tended to be moderated by the federal agencies, which have long held bipartisan leadership. And federal law forbade the president to fire the regulators without cause.

Now more volatile policy-making could lie ahead as a result of the court decision, former corporate executives, former regulators and legal experts warned. Many companies plan for expansions and investments years in advance, and regulatory uncertainty often stifles growth.

“Stability is the most important thing,” said Samuel J. Palmisano, a former chief executive of IBM and now a board member of a venture fund, America’s Frontier Fund. The decision “will slow down innovation.”

The independent agencies affected by the court’s decision include the Federal Trade Commission, which works to protect consumers from practices like deceptive advertising or those harmful to competition; the Federal Energy Regulatory Commission, which oversees interstate power lines, natural gas operations and regional power grid operators; the Surface Transportation Board, which regulates railroad rates; and the National Labor Relations Board, which resolves disputes between employees and employers.

Commissioners leading the agencies — traditionally a mix of Republicans and Democrats — are appointed by the president. In 1935, the Supreme Court ruled that the president could not fire the regulators over political or policy differences.

That held until last year, when Mr. Trump dismissed Democratic commissioners at agencies including the Federal Trade Commission, the National Labor Relations Board and the Surface Transportation Board.

Rebecca Kelly Slaughter, a fired F.T.C. member, took her case to the Supreme Court, saying she had been wrongfully terminated. The court ruled against her last week.

A spokesman for the F.T.C., Joe Simonson, said the agency offered “clarity for the business community that was under assault by the previous administration’s left-wing ideologues.” He added, “There is nothing novel about President Trump’s position as the rightful leader of the executive branch, which the court affirmed.”

Some regulatory experts and corporate advisers said it was unclear how much — if at all — the ruling might shift the agencies’ political agendas. Even when independent, most regulators adhered to the White House’s policies, they said.

“The notion that Slaughter is a big deal because it gives the president more composed power over the policy agenda is exaggerated,” said Joseph Grundfest, who was a commissioner at the Securities and Exchange Commission in the 1980s and is now a law and business professor at Stanford.

But the agencies have traditionally ignored politics when taking legal action, he said. The White House could now assert greater control over decisions like whether to sue a company over insider trading.

Companies are trying to plan ahead, said Matthew L. Schwartz, the chairman of the law firm Boies Schiller Flexner.

“They’re doing what smart people and smart companies do, which is solicit input from a lot of knowledgeable people about what might be coming around the corner so they can try and do some contingency planning,” said Mr. Schwartz, who has represented companies including the fantasy sports app DraftKings and the insurer AIG.

The president’s new ability to remove decision makers at federal agencies could lead to big changes in crucial sectors of the economy.

Two freight rail companies, Union Pacific and Norfolk Southern, last year proposed a merger that would create the nation’s first single network connecting the East and West coasts, a deal that requires approval by the Surface Transportation Board. Last year, Mr. Trump fired Robert E. Primus, a board member who had voted against another big rail merger in 2023.

With Mr. Primus’s removal, Union Pacific and Norfolk Southern may have a better chance of getting the board to approve their merger, some rail analysts have said. A spokeswoman for the board declined to comment.

Some consumer advocacy groups are concerned about the potential impact of a partisan Federal Energy Regulatory Commission on energy prices.

“FERC has really been through Republican and Democratic administrations and really worked hard to be nonpartisan,” said Tyson Slocum, the director of the energy program at Public Citizen, a consumer advocacy group. “What the Supreme Court has done is toss that aside.”

The ruling also has implications for companies with business before the N.L.R.B., which includes adjudicating labor practice cases and recognizing new unions.

If the agency loses — or even appears to lose — its political independence, or seems beholden to the president, unions and companies will be less trusting of its rulings, labor experts said. State labor agencies may try to step in to fill the void, which could create a patchwork of conflicting rules.

Companies have already scrambled over the past year and a half to curry favor with the Trump administration. Mr. Trump’s new power to fire regulators who don’t align with him may accelerate that, corporate experts said.

Many companies have already sought out connections with Mr. Trump’s inner circle or made donations to his inauguration, his library or other pet projects, said Jill Zuckman, a partner at SKDK, a public affairs firm.

“It’s going to supercharge what a lot of companies have been doing,” said Ms. Zuckman, who represents tech and transportation companies and worked for the Obama administration.

Reporting was contributed by Ivan Penn from Los Angeles, Jordyn Holman from Chicago, and Peter Eavis, Lauren Hirsch and Rebecca Davis O’Brien from New York.