MEXICO CITY >> All is not well in the kingdom of Carlos Slim.

For more than 25 years, he has dictated the terms of Mexico’s telecommunications industry and built an empire, making him one of the world’s richest men.

Slim and his family are billionaires 50 times over. He has stood at the very top of the Forbes World’s Billionaires list — more than once. His flush years in Mexico enabled him to span the Americas with companies that touch nearly every facet of modern life: telecom, banking, construction, retail and media, among others.

But at home in Mexico, the game is changing. And there is not much he can do about it, analysts say.

Determined to bring his dominance to an end, leaders from Mexico’s three biggest political parties have put aside their own animosities in recent years, meeting in secret sessions to chip away at Slim’s domain.

Now, the plan they concocted to increase competition in the telecommunications industry, signed into law two years ago, is starting to bite.

Profits for Slim’s flagship company, America Movil, are in steep decline, falling 24 percent in 2015 and almost 44 percent in the first six months of this year, compared with the year-earlier periods. A closely watched metric of profitability on Wall Street has also fallen, and the company’s stock has dropped by 39 percent in the past year.

In its quarterly report last month, the company acknowledged that increased competition was crimping profits in Mexico. Under the new law, it must submit to special rules as the dominant phone company. It cannot charge fees to its smaller competitors when their users call into its network and it must share its infrastructure, including cell towers, all of which Slim says forces him to subsidize behemoths like AT&T.

“What has changed the most and is most relevant here is the authorities, and their attitude toward this empire,” said Ernesto Piedras, the director general of the Competitive Intelligence Unit, a consulting and research firm. “This is the first time Slim does not have a copy of all the keys.”

Regulators in Mexico, sometimes against their government’s wishes, had tried for decades to rein in Slim’s dominance, finding themselves thwarted at every turn.

His monopoly was so dominant that it cost Mexicans an extra $13 billion a year between 2005 and 2009, according to the Organization for Economic Cooperation and Development. Still, his wealth, armies of lawyers and government connections kept him a step ahead of weak regulators, former officials say.

But when the Institutional Revolutionary Party took back the presidency in 2012, it looked to reassert its power in a country where the state — not big businesses — has traditionally been king. And Slim offered a way to score political points at the same time: Mexicans were already openly scornful of what they called his expensive and often unreliable service.

Overhauling telecom was a crucial part of President Enrique Pena Nieto’s push to recast the image of Mexico and his party, which had governed the nation for seven decades before losing an election for the first time in 2000. He vowed a new Institutional Revolutionary Party, dedicated to recharging the economy. He promised a new era, declaring it “Mexico’s moment.”

The celebration was short-lived, with corruption and security scandals sinking Pena Nieto’s approval ratings to the lowest of any president in a quarter-century. But the economic overhauls continued. Mexico is inviting private companies to drill for oil. Changes to the school system are underway. And Slim is facing effective competition for the first time.

For Mexico, the telecom law offers a stark contrast to the state’s many failed promises — to end corruption, enact the rule of law and bridge inequality. That the government has managed to take on Slim, arguably the country’s most powerful citizen, is proof that where there is political will in Mexico, there is a way.

“This administration invested in the economic reforms, but they ignored the reforms in the judicial system and in the field of corruption,” said Enrique Krauze, a prominent Mexican historian who knows Slim.

Still, the changes have done little to dent Slim’s market share. He retains nearly 70 percent of the cellphone market and about 65 percent of fixed lines.

In an interview, Slim said the new law established a certainty that all businessmen appreciate. But he bristled at the notion that his company required special regulation, or that it had stalled or impeded regulation in the past.

“Look at all the regulation they have imposed on us. Look at them!” he said. “Every time they complain about something, they lobby to impose a regulation.”

Slim acknowledged that profits were down. Currency woes in Latin America have taken a heavy toll. And the recent entry of AT&T, which has promised to spend billions to compete with his company, has helped bring down cellphone plan prices significantly, including his own. Through it all, Slim said, his customers have stayed with him.

“They thought they would come and bulldoze us, just because they are called AT&T,” he said. “On the one hand, they say ‘the biggest network in North America,’ and on the other, they say that because they are small here we should subsidize them.”

This year, Mexican regulators will determine if the new measures are enough to curb Slim’s dominance. Regulators can crack down further if they decide América Móvil is not opening up to competition — by imposing large fines or even ordering its breakup.

Overall, Slim appeared sanguine about his prospects.

“I have said it various times: Telecommunications are the nervous system of the new civilization,” he said. “You have to have a medium and long-term vision. You can’t have quarterly visions.”

Not all analysts share his view.

“The worst is not yet over,” said Andre Baggio, an analyst at J.P. Morgan.

Opportunity called

Even before he became a household name in Mexico, Carlos Slim was a wealthy man. During the turmoil of the 1980s, a time of severe debt crises often called Mexico’s lost decade, he had grown rich by snapping up bankrupt firms.

As the country slid further into economic depression, Slim was the rare businessman with deep pockets. So President Carlos Salinas, under pressure in 1990 to sell off state-owned companies, dispatched a top official to gauge Slim’s interest in buying the national phone company, Telefonos de Mexico.

The pitch was straightforward: Whoever bought the company would receive a temporary monopoly. In exchange, the winner would have to invest billions in a company so decrepit that Mexicans never knew whether they would get a dial tone.

Slim seemed skeptical. Still, he smelled opportunity.

“If I enter and win, it’s going to change my life,” Jacques Rogozinski, the Mexican official in charge of the sale, recalled Slim saying.

And so it did.

There are many stories of Carlos Slim’s rise: the son of Lebanese immigrants who inherited a family retail business and built an empire, piece by piece, down the long Latin American stretch of the Western Hemisphere. Those vast holdings include a significant number of shares in The New York Times.

But there is another side, officials say — of tying up regulation in countless legal knots, of befriending the rich and powerful who identified his success with their own.

This assertion enrages Slim, who denies stymying regulation. Ultimately, it comes down to customer choice, he said, in Mexico or anywhere else.

“You can’t, in a market of 110 million consumers, hold on unless people prefer to stay with you,” he said.

Shortly after winning the bid for Telmex, as the national phone company is called, Slim got to work improving service with his original partners, Southwestern Bell and France Telecom, both of which later sold their stakes in the partnership. They installed millions of phone lines, and curtailed the common practice of repairmen asking for bribes.

For years, the government left Slim to tend to the monopoly without interference. He was building something bigger than a company. As one of the first major emerging market stocks, Telmex was seen as a bellwether for an entire asset class on Wall Street. Hurt Telmex, the logic went, and you could hurt the market’s perception of Mexico.

But eventually, there was dissension in the ranks. Officials entrusted with policing competition in Mexico tried to rein him in. In 1997, the Mexican Federal Competition Commission ruled that Telmex was too powerful.

Shortly before the ruling, the head of the commission, Fernando Sanchez Ugarte, got a call from a nervous senior official.

“This will destroy the stock market,” he recalled the official telling him.

Slim’s appeals of the ruling lasted a decade, until a judge decided in his favor. The regulators — outnumbered, outspent and trying to enforce weak laws — never stood much of a chance, former officials said.

Regulators recall how Slim’s lawyers would file into a conference room, wheeling large boxes of documents for routine meetings. At least once, the phalanx of lawyers was told to wait outside because the room was too small.

“The story is not about Slim,” said Robert K. Lacy, who was in charge of regulatory issues for Avantel, an early competitor to Telmex. “The government just buckled.”

Slim said he never meant to tie up the system or compete unfairly. Rather, he said, when faced with an unjust fine or restriction, he simply fought back.

Beyond Mexico

Slim is often likened to Warren Buffett for his relatively low-key, avuncular style. He still lives in the modest home where he raised his children and drives himself around town, unlike many in Mexico’s minted class.

Years ago, on a visit to one of his ubiquitous Sanborns department stores, Slim spotted one of Mexico’s most renowned poets, Homero Aridjis, reading a newspaper for sale in the store.

Slim insisted he buy it.

“He doesn’t believe anything should be for free,” said Aridjis, adding that Slim eventually backed down.

Rather than hosting lavish spreads for meetings, Slim sometimes just orders in from Sanborns, whose aesthetic is reminiscent of an older generation of American diners.

His reach extends far beyond Mexico, gained with an ability to time investments well and then exploit every opportunity to bolster them.

He swept into Brazil in 2000, buying up cellphone companies to create a national one. He then fought a nearly decade-long lawsuit by the investment arm of Brazil’s state-owned development bank, and waited patiently for lawmakers to let foreigners increase their control over pay television.

It was classic Slim. Today, Brazil is America Movil’s largest subscriber market — larger even than Mexico.

His strategy included building a close relationship with the president at the time, Luiz Inacio Lula da Silva, who now faces obstruction charges in an enormous corruption probe. Slim has not been accused of any wrongdoing.

It was not the first time Slim befriended a president. In Panama, he made fast friends with Martin Torrijos, flying down for meetings, sharing dinners and even lending him a jet to attend the funeral of Pope John Paul II.

Panama represented an opening, and Slim wanted in. After years of stagnation under the dictatorship of Manuel Noriega, Panama pinned its hopes on investment. Slim, in turn, saw a chance to expand his cellphone empire and win contracts for the expansion of the Panama Canal.

He managed both, but Slim wanted more: a concession to build and operate a hydroelectric power station. There was one problem. The rights belonged to someone else, an entrepreneur named Julio Cesar Lisac, who had acquired 50-year concessions for two dams in 2005.

Then, one day, a Mexican engineer paid Lisac a visit.

The engineer worked for the Mexican state electric utility, whose chief executive was the brother of Slim’s son-in-law. It was an odd visit. The Mexican state utility cannot build or finance projects outside Mexico. Lisac said it became clear that the real suitor was Slim.

Eventually, representatives of an infrastructure company Slim controls made an offer. Lisac refused.

“Slim’s no fool,” he said. “He knew we had good dams in a good location.”

Slim wound up with the project anyway. After missing a deadline, Lisac had the concession stripped from him in 2006. Less than two years later, it was awarded to Slim’s company.

Lisac fought in Panama’s Supreme Court — and won — but regulators refused to enforce the order. By that time, 2010, Slim had already built the power station and was operating it.

Lisac suspected that Slim’s growing relationship with President Ricardo Martinelli, a supermarket magnate elected in 2009, could be at play. Slim and Martinelli maintained friendly relations, including attending the final New York Yankees game of the great Panamanian pitcher Mariano Rivera together.

Refusing to give up, Lisac went before a World Bank court in 2013, but it rebuffed his challenge this June, calling it a domestic Panamanian dispute.

Slim denied foul play, noting that he and his company had won the concession in a government auction.

“The government of Panama has won this lawsuit; it’s closed,” Slim said.

Suspending investment

Slim has not always prevailed. In 2011, he paid a visit to regulators who had just won a decision in Mexico’s Supreme Court that was about to cost him a lot of money.

The ruling cut into an important income stream for Slim, forcing him to accept vastly reduced fees from other cellphone carriers for calls into his networks. He had fought the cuts for years, and told regulators they were making a mistake.

But public opinion was turning against him.

While Slim invested heavily in Mexico’s phone service in the early years, the pace slackened significantly by the 2000s. Service suffered, but not profits. In 2008, the Organization for Economic Cooperation and Development report found, America Movil’s profit margin was nearly 70 percent higher than the average in other member countries.

Mexico also lagged its Latin American peers in expanding mobile broadband service to all its citizens, falling behind Brazil, Argentina, Colombia and even Venezuela, according to 2014 figures from the Broadband Commission for Sustainable Development, a United Nations initiative.

Slim is one of the commission’s co-chairmen. Asked why rural stretches of his country have no cellphone reception, he cited regulators.

“They began to insist that we have a lot of market share and that it was a reason to regulate us,” he said. “We suspended investment in places where we would have 100 percent of the market” because it would invite more regulation.

Many Mexicans felt they were paying more for less, creating an opening for the new government. As Pena Nieto took office in 2012, a plan was hatched.

The government and Mexico’s three major parties met secretly, choosing different locations around Mexico City, often late at night, to avoid word leaking out until the legislation was almost ready.

They also took aim at Mexico’s two dominant television companies, which had been equally aggressive in protecting their market shares.

Once a deal was reached, lawmakers enshrined the law in the Constitution to head off Slim’s legal challenges, and set up special courts to rule on them.

‘Three moves ahead’

Those who know Slim say he has long anticipated the day when his control of Mexican telecom would diminish.

“He knew this was coming,” said James R. Jones, a former U.S. ambassador to Mexico during the 1990s. “And I suspect he was planning three moves ahead.”

While Slim’s dominance — and profits — may be under threat in Mexico, his wealth no longer depends on it.

“He began to invest in other things,” said Juan Molinar, a former communications minister, in an interview before he died last year. “Follow the money.”

And for years, the money has flowed elsewhere.

In the United States, the results have been mixed. An investment in the retailer CompUSA was a failure, while a repaid $250 million loan to The New York Times made a handsome investment. He is now the company’s largest shareholder (Slim holds Class A shares, which have limited voting rights).

His companies build and lease offshore rigs, drill wells, operate dams in Panama and build gas pipelines in Mexico and the United States. He is even doing business with Halliburton’s most famous alumnus, Dick Cheney, investing alongside the former vice president in WellAware, a Texas oil services software startup.

Mexico’s $13 billion airport project has his fingerprints on it, too, including a son-in-law in partnership with the chief architect and another relative by marriage who served on the design committee.

Though the committee member recused himself, the local news media saw what it often sees: “The New Mexico City Airport Will Have the Stamp of Carlos Slim,” as one headline put it.

© 2016 The New York Times Company