U.S. Special Counsel Robert Mueller has a distinctly modern problem. The chairman, judging by his tweets, could try to pardon people in his circle even before attorneys charge anyone who knows a crime.

Mueller’s all-star team of prosecutors, with expertise in fund laundering and foreign bribery, has an answer to that. He’s Michael Dreeben, a bookish career government lawyer with more than 100 Supreme Court appearances under his belt.

Dreeben with a jersey celebrating the number of his U.S. Supreme court appearances.

Source: National Association of Former United States Attorneys

Acting as Mueller’s top legal counsel, Dreeben has been researching past pardons and determining what, if any, restrictions exist, according to person or persons very well known the matter. Dreeben’s broader brief is to make sure the special counsel’s prosecutorial moves are legally airtight. That could include anything from strategizing on novel interpretations of criminal matters to constructing sure the most recent search warrant on ex-campaign adviser Paul Manafort’s home would stand up to an appeal.

“He’s seen every criminal case of any outcome in the last 20 years, ” said Kathryn Ruemmler of Latham& Watkins LLP, who served as White House counsel under President obama. “If “youre trying to” do a no-knock warrant, he’d be a great guy to consult with to determine if you two are exposing yourself .”

Three Decades

Dreeben, 62, built that expertise over three decades as appeal procedures lawyer at the Justice Department. As a deputy solicitor general, he’s pored over attorneys’ moves in more than a thousand federal criminal prosecutions and protected many of them from challenges all the way to the nation’s highest court.

Dreeben has begun working on legal issues as a counselor to Mueller but is also retaining some of his solicitor general work for the sake of continuity, according to Peter Carr, a spokesman for the special counsel’s office. Carr declined to elaborate on Dreeben’s work with Mueller or induce Dreeben available for comment.

Pre-emptive forgiveness are a distinct prospect now that current and former Trump advisers are under Mueller’s scrutiny. Trump himself has tweeted that everyone agrees the U.S. chairperson has ” complete power to pardon.” Some of those kinds of executive moves have been well analyzed, including Gerald Ford’s swift pardon of Richard Nixon and Bill Clinton’s exoneration of fugitive financier Marc Rich. But the legal territory is largely uncharted over pardons of a president’s own campaign laborers, own family members or even himself — and how prosecutors’ operate would then be affected.

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What Dreeben brings to the question, say those who know him, is a credibility that comes from parsing how criminal prosecutions have played out across the country. A balding and bearded New Jersey native with a somewhat nasal delivery, he has a knack for constructing careful arguments and the eloquence in tribunal to lay them out in well-reasoned paragraphs, said Miguel Estrada, a lawyer at Gibson Dunn& Crutcher LLP.

His path wasn’t precisely aim. Dreeben intended to pursue an advanced degree in history at the University of Chicago before changing his thinker and enrolling at Duke University School of Law, according to a profile of him last year in Law3 60. He studied at Duke under Sara Beale, who’d operated in the Solicitor General’s office and helped flower the relevant recommendations of representing the U.S. in controversies before the country’s highest court.

Click here to watch a video of Dreeben committing a talk at Duke Law in 2010

Dreeben got his first shoot in 1989. His antagonist before the Supreme Court was another first-timer, a private practice lawyer named John Roberts.

Dreeben lost. But the moment left an impression on Roberts , now the court’s Chief Justice. After Dreeben attained his 100 th statement before the court last year, Roberts called him back to the lectern, recollecting the decades-earlier meeting.

” You have consistently advocated points on behalf of the United States in an exemplary way ,” Roberts said, extending the court’s appreciation for his” several years of advocacy and dedicated service .”

Dreeben had exhorted the court the working day to uphold the conviction of former Virginia governor Robert McDonnell on accusations of public dishonesty. The Supreme court ultimately overturned McDonnell’s conviction.

Dreeben’s reviews of how instances were built against McDonnell and others will be invaluable to Mueller. Appellate lawyers like Dreeben are stayed with decisions already made at the prosecutorial degree, said Estrada, who worked in the Solicitor General’s office in the 1990 s. But now, he added, Dreeben is in a position to troubleshoot troubles before cases are filed.

” You have to argue what you’ve got, and the cake is already baked ,” Estrada said. On Mueller’s team, by contrast, Dreeben” has the opportunity to measure the flour .”