Shortly after Jonathan Kanter took over the Justice Division’s antitrust division in November 2021, the company secured a further $50 million to analyze monopolies, bust felony cartels and block mergers.

To rejoice, Mr. Kanter purchased a prop of an enormous verify, positioned it exterior his workplace and wrote on the verify’s memo line: “Break ’Em Up.”

Mr. Kanter, 50, has pushed that philosophy ever since, changing into a lead architect of probably the most vital effort in a long time to battle the focus of energy in company America. On Thursday, he took his greatest swing when the Justice Division filed an antitrust lawsuit in opposition to Apple. Within the 88-page lawsuit, the federal government argued that Apple had violated antitrust legal guidelines with practices supposed to maintain prospects reliant on its iPhones and fewer prone to change to competing units.

That lawsuit joins two Justice Division antitrust circumstances in opposition to Google that argue the corporate illegally shored up monopolies. Mr. Kanter’s employees has additionally challenged quite a few company mergers, together with suing to cease JetBlue Airways from shopping for Spirit Airways.

“We need to assist actual individuals by ensuring that our antitrust legal guidelines work for staff, work for customers, work for entrepreneurs and work to guard our democratic values,” Mr. Kanter mentioned in a January interview. He declined to touch upon the Google circumstances and different energetic litigation.

At a news conference concerning the Apple lawsuit on Thursday, Mr. Kanter in contrast the motion to previous Justice Division challenges to Commonplace Oil, AT&T and Microsoft. The swimsuit is geared toward defending “the marketplace for the improvements that we will’t but understand,” he mentioned.

Mr. Kanter and Lina Khan, the chair of the Federal Commerce Fee, have now taken motion in opposition to 4 of the six greatest public tech firms, in a sweeping drive to rein within the energy of the trade. The F.T.C. has individually filed antitrust fits in opposition to Meta, the proprietor of Fb and Instagram, and Amazon.

However Mr. Kanter and Ms. Khan are on the clock to see how far they’ll take their efforts. The November election might take away President Biden from the White Home and take Mr. Kanter and Ms. Khan with him.

Greater than two dozen individuals who know Mr. Kanter, together with present and former Justice Division workers, described his two-decade rise. Some spoke anonymously to explain confidential authorities deliberations and displays.

Mr. Kanter was raised within the Queens, N.Y., house the place his dad and mom nonetheless dwell. After graduating from Forest Hills Excessive Faculty, he attended the State College of New York at Albany after which regulation college at Washington College in St. Louis.

“I grew up in a neighborhood with schoolteachers and cops and taxicab drivers and shopkeepers and individuals who labored actually arduous,” he mentioned, and did so with a “perception that the American dream actually offered openings and alternatives to comprehend a greater life for future generations.”

He mentioned he linked antitrust enforcement to these values as a result of “it’s about ensuring that these alternatives can be found to all and ensuring that folks can succeed on their very own deserves.”

After getting his regulation diploma, Mr. Kanter labored on the F.T.C. earlier than becoming a member of massive regulation corporations like Cadwalader, Wickersham & Taft and Paul Weiss. At one level, he represented Microsoft. When the corporate mounted an offensive in opposition to Google, which had eaten its lunch in on-line search, Mr. Kanter made the pitch round Washington that Google deserved further scrutiny.

He later made comparable arguments for different Google critics, like Information Corp and Yelp, and mentioned regulators ought to examine further tech giants, too. Concurrently, he defended company mergers in separate industries.

Mr. Kanter’s work in opposition to a number of the tech behemoths received him followers amongst those that believed that antitrust legal guidelines have been a vital device to make the economic system extra honest.

“Right here was an insider who had additionally come to very comparable conclusions,” Ms. Khan mentioned in an interview in November.

After his nomination by Mr. Biden was confirmed, Mr. Kanter, who usually favors formal peak lapels and as soon as wore to a photo shoot an A. Lange & Söhne gown watch that retails for $34,500, debuted his plan for the antitrust division to its employees, individuals with information of the presentation mentioned.

Mr. Kanter branded his initiatives with catchy code names. A plan for the company to shortly weigh in on energetic authorized circumstances received the Gen Z moniker “Actual Time AF,” quick for real-time antitrust filings. He referred to as a plan to analyze senior company executives the “Billionaire Accountability Undertaking.”

Mr. Kanter informed his staff that, at any given second, he wished the division to have the ability to handle 30 civil lawsuits and one other 30 felony circumstances. He referred to as the plan “30 for 30.”

The company was already stretched skinny, and a few on the employees felt Mr. Kanter was setting unreasonable targets, individuals with information of the matter mentioned.

His time in personal follow additionally solid a shadow. Mr. Kanter initially didn’t work on lawsuits in opposition to Google as a result of he had spent years representing its rivals. When he can’t work on circumstances, together with the problem to JetBlue’s buy of Spirit, they’re led by his principal deputy, Doha Mekki.

Nonetheless, Mr. Kanter has been proactive on the fits in opposition to the tech giants.

As a Google antitrust case over on-line search headed to trial final 12 months, he informed authorities legal professionals to be extra specific and outstanding with their argument that sheer scale of the corporate’s operation entrenched its energy and made it tougher for its rivals to compete, two individuals with information of the matter mentioned. That concept was a central theme when the case was tried in a Washington courtroom final fall. (A ruling is predicted later this 12 months.)

Mr. Kanter additionally oversaw the ultimate months of the Justice Division’s investigation into Google’s management of internet advertising know-how. He argued to colleagues that the federal government ought to push for the lawsuit to be determined by a jury as an alternative of a decide, which has been the norm in comparable civil circumstances, an individual aware of the matter mentioned. A jury trial is scheduled to start out in September.

Mr. Kanter’s work has been scrutinized by critics who surprise if he and his compatriots are pushing the boundaries of antitrust regulation too far, hurting the economic system.

William Kovacic, a regulation professor at George Washington College and former chair of the F.T.C., mentioned Mr. Kanter had but to safe a victory within the form of sweeping monopoly lawsuit that the company was pursuing in opposition to Apple and Google.

“In some methods, he’s nonetheless in search of that extra outstanding trophy to go on the mantelpiece,” he mentioned. “You win one in all these monopolization circumstances, you possibly can take the remainder of the last decade off.”

Within the January interview, Mr. Kanter defended his push to shift how the company did enterprise. He mentioned the world had modified radically within the final 30 years. Folks talk utilizing new mediums, get their info from totally different sources and conduct commerce on ascendant platforms.

“It’s essential that if we’re going to have antitrust enforcement that’s fit-for-purpose in a contemporary economic system we acknowledge these adjustments,” he mentioned. “After which we adapt to ensure that we’re imposing the letter of the antitrust regulation and the relevant precedents. However we’re imposing the regulation in a approach that displays the realities of immediately’s economic system.”

Tripp Mickle contributed reporting from San Francisco. Jack Begg contributed analysis.