It's been a busy couple of years for the white collar and regulatory defense teams at Paul, Weiss, Rifkind, Wharton & Garrison.

A longtime white collar presence, the firm has remained a go-to option for corporate boards and executives facing legal peril. From helping the independent directors at Tesla through the U.S. Securities and Exchange Commission's investigation of Elon Musk's tweet announcing the company would be taken private to helping real estate businessman Nicholas Schorsch through a criminal investigation and several related lawsuits, the firm has helped clients in industries both old and new minimize their legal risks and avoid liability.

While most of the firm's lawyers are in Manhattan, it has taken on legal challenges across the globe. From the Justice Department in Washington, D.C., whose antitrust division gave Paul Weiss client Cigna the all-clear to acquire Express Scripts Inc. while an earlier announced tie-up between Aetna and CVS Health was still under review, to Japan, where longtime chair Brad Karp and colleagues have defended former Nissan CEO Carlos Ghosn from a harsh system with a famously high conviction rate, Paul Weiss has seen its share of complex and headline-grabbing cases.

But for Lorin Reisner, who co-chairs the firm's white collar and regulatory defense practice, some of the cases he's proudest of were the ones that didn't make waves. Despite the pressure government attorneys face to bring a case after long, resource-intensive investigations, he says, he secured four decisions not to sue from the SEC in a seven-month period, from October 2017 to April 2018. One declination was secured after a four-year probe, he says.

Some of the firm's work has been more traditional, like its representation of Schorsch, who led the real estate investment trust known as Vereit during a period when it was consumed by an accounting scandal. He never faced criminal charges, even as Vereit's chief accounting officer, Lisa McAlister, pleaded guilty and its chief financial officer, Brian Block, was convicted. Schorsch settled with the SEC in July 2019, but the agency agreed to take payment in illiquid assets and there was no officer or director bar imposed as a condition of the deal, Reisner says.

Other matters had novel aspects. The firm defended ExxonMobil through several investigations and lawsuits over its role in climate change, including a securities fraud case brought by New York's attorney general and common law nuisance cases brought by several cities, winning dismissals in several of them. The state securities enforcement case recently went to trial before Justice Barry Ostrager and a ruling hasn't yet come down.

Finalists: Covington & Burling; Gibson, Dunn & Crutcher; Sullivan & Cromwell.

Paul Weiss also represented the NBA's Philadelphia 76ers (whose main owner, Joshua Harris, co-founded firm client Apollo Global Management) in an investigation of several anonymous Twitter accounts that had been linked to a team executive. In a whirlwind, weeklong probe, the firm conducted interviews and forensic investigations that determined the executive's wife was behind most of the accounts.

"I probably got two hours of sleep or so a night during that investigation, but it was fascinating," Reisner says.

And with leading politicians calling for more aggressive antitrust enforcement, clients in a broad sweep of industries have turned to partners like Charles "Rick" Rule for help with deals and conduct that raise concerns of abuse of market power. Rule and his colleagues have continued to handle major work for the Japanese electronics manufacturer Nippon Chemi-Con, which talked its way down to a $60 million fine last year after it took issue with the involvement of a conflicted Justice Department attorney on the case. Paul Weiss has defended the company through related civil litigation.

The practice also secured a major win in the $67 billion Cigna-Express Scripts merger. Despite concerns from some investors that the government's opposition to vertical mergers, like AT&T's bid for Time Warner, could kill Cigna's effort to buy ESI, Rule says he and his colleagues showed the market and regulators that the deal was legal.

"There were people out there in the marketplace who said, 'Oh my goodness, you're going to be caught up in the AT&T-Time Warner theory," he says. But by asking a former Antitrust Division chief economist to speak with investors, and by pursing a "full-court" approach with regulators, the deal was speedily approved, he says.