Lawyers from the Justice Department and AT&T gathered in a small Washington courtroom Thursday to meet the judge who will oversee their legal battle, one of the biggest antitrust cases in decades.

As Judge Richard Leon lumbered into the room, assembled before him were two conference tables full of attorneys for both sides. In the first row of the audience sat Makan Delrahim, the Justice Department’s antitrust chief.

“This is not a normal case,” said Leon, speaking with traces of the accent he picked up during his childhood in South Natick, Mass. “And I’ve had a number of big ones, as some of you know.”

Leon is no stranger to high-profile cases. Appointed to the U.S. District Court for the District of Columbia by George W. Bush in 2002, the candid judge has presided over controversial cases involving Guantanamo detainees and the surveillance powers of the National Security Agency.

The parties responded to the judge in a light and respectful manner, but Leon repeatedly stressed how it’d be the parties’ responsibility to ensure the proceedings run smoothly. “We can’t take a blizzard of paper,” he said. “I don’t have 29 associates. This is not my only case.”

Leon scheduled the trial over the telecom giant’s proposed $85 billion takeover of Time Warner for March 19. Leon warned both sides not to expect a final decision in the case before April 22, a key deadline that AT&T and Time Warner set for themselves as part of their deal. The two must close the deal by then or AT&T must pay Time Warner $500 million.

“This is not a case where people’s liberty has been taken, but it is a case where the stakes are huge,” Leon said. “The people who are in, are all in — including me.”

Leon is known in the legal world as a maverick, with strong opinions and no clear political allegiance. He sometimes berates lawyers and favors bow ties. His boisterous cackle can be heard from a distance.

While it’s not clear how he will apply his past thinking to this case, antitrust experts say that you can get a sense of how it might unfold by looking at another telecom acquisition the judge oversaw in 2011. Back then, Comcast was seeking to finalize a multibillion-dollar deal to purchase NBC Universal, a similar type of merger involving a content company and a content distributor. While the government did not move to block that deal, the Justice Department and Comcast had to appear before a federal judge and come to a settlement with certain conditions before the acquisition was completed.

In what was considered by antitrust lawyers at the time as an unusual move, Leon expressed skepticism over the conditions of the settlement; judges overseeing such agreements typically approve them without protest. Leon took issue with an arbitration process that would theoretically allow online content distributors to challenge Comcast over anti-competitive practices. Specifically, Leon doubted how well that arbitration mechanism would work for potentially wronged Internet companies, and whether the government could enforce the terms of the agreement. Ultimately, Leon approved the deal. But not without tying in auditing requirements.

Other experts pointed to how Leon handled the NSA and Guantanamo Bay cases as indicators of his independent thinking and his disregard for cultivating popularity. In 2013, he put the Obama administration and the intelligence community on the defensive after he ruled that the NSA’s daily collection of virtually all Americans’ phone records is probably unconstitutional. And in 2008, during Bush’s final year in office, Leon was the first federal judge to order the release of detainees from the U.S. military prison at Guantanamo Bay, after concluding that the government had failed to prove that five Algerian men were enemy combatants under the government’s own definition.

“Leon is a character,” said one lawyer who asked not to be named because that person practices in the DC circuit and may appear before Leon. “He tends to be very loud and aggressive from the bench. He also tends to move cases along more speedily than many district judges, to his credit.”

“If Judge Leon asks you a question, you must be prepared to answer it candidly and directly,” said Charles Leeper, a partner at the law firm Drinker Biddle, who has appeared before Leon several times.  “If he perceives evasiveness or dissembling in your response, you are lost.”

Before becoming a judge, Leon worked in private practice and at the Justice Department. In the 1980s, Leon advised then-Rep. Richard B, Cheney during the Iran-contra investigation, which focused on the provision of arms to Nicaraguan fighters with funds obtained by weapons sales to Iran.  He was a special counsel to the House Banking Committee during its Whitewater investigation. He is an adjunct law professor at George Washington University, as well as Georgetown Law, where he teaches a class on congressional investigations with John Podesta, former chairman of the 2016 Hillary Clinton campaign. “I deposed him during the Whitewater investigation, the summer of ’94,” Leon told the Washingtonian last year. “Which is usually not the basis of a friendship,” Podesta said in a feature about odd-pair friendships in the often-polarized national capital.

And now he’s set to oversee the monumental AT&T and DOJ case. For this legal battle, the burden is on the Justice Department to convince him that the deal will substantially lessen competition, experts say. AT&T will still try to make a positive case that its proposed merger will serve the public interest, according to Harry First, an antitrust specialist at New York University School of Law. “You do want to put in front of someone the feeling that you should not stop this, that it will benefit consumers.”

Mark Abueg, a spokesman for the Justice Department, said in a statement, “DOJ is looking forward to its day in court on behalf of the American consumer.”

AT&T said it appreciated that the court was expeditious about the timing of the trial. “We are committed to this transaction and look forward to presenting our case in March,” said David McAtee, AT&T’s general counsel.

Leon’s chambers did not immediately respond to a request for comment.