On Thursday afternoon, William Barr became the most important person in America when it comes to determining the fate of special counsel Robert Mueller’s final report.

Barr, who was sworn in Thursday as the new Attorney General of the United States, will make the call about who gets a copy of the report inside the leak-prone Trump administration. He will decide how hard it is for Congress to tap Mueller’s work for its own probes. Barr could even try to block access to court materials by outsiders.

Which means all told, no figure will have such singular influence over the fallout from Mueller’s final report, including how much damage it may do to the President himself.

Here are three ways Barr will make decisions that determine the fallout from Mueller’s report, from the White House and the Justice Department to Congress to the courts.

He decides how much of the report goes to Congress and the White House

Barr has unique power over what aspects of Mueller’s report to share. The regulation about Mueller’s final report says, “At the conclusion of the Special Counsel’s work, he or she shall provide the Attorney General with a confidential report explaining the prosecution or declination decisions reached by the Special Counsel.” Read literally, that means the only person Mueller’s report must go to is Barr.

During his confirmation hearing, Barr pledged that he would provide Congress with at least some information about Mueller’s findings. “I also believe it is very important that the public and Congress be informed of the results of the special counsel’s work,” he said during his opening remarks to the Senate Judiciary Committee on Jan. 15. “For that reason, my goal will be to provide as much transparency as I can consistent with the law.”

But Barr has broad discretion over what he deems appropriate to send to Congress, and if he writes a summary of Mueller’s findings, how detailed that summary should be.

Barr’s control over the report is so broad, there is even uncertainty about what he might choose to share with the White House. It’s unclear at what point in the process the White House would have the ability to review the report, according to one White House official. Mueller could send his full report straight to the White House at the same time he sends it to Barr, but Mueller is a literalist when it comes to rules. “I’d be surprised if the special counsel did that without at least clearing it with the attorney general first,” says John Bies, chief counsel at American Oversight. So again, the authority will rest with Barr.

Some legal experts are skeptical of the idea that the Mueller report could ever be withheld from the president and his lawyers entirely. “The regs don’t say, ‘You must send it to the White House first,'” says Victoria Toensing, a Washington lawyer who was in talks to join Trump’s team last year. “But they do say to send it to the attorney general, and the person who supervises the attorney general is the president, so it would go there.”

He can thwart Congressional efforts to get to Mueller to testify

In an interview with TIME in December, House Judiciary Chairman Jerrold Nadler said if he didn’t get a copy of the Mueller report, they might subpoena it or ask Mueller to testify.

But either move would likely end up in the courts. And if Barr wanted to block them, Congress wouldn’t have great options. “Enforcing congressional subpoenas means protracted civil litigation,” Harry Litman, former deputy assistant attorney general, wrote in the New York Times op-ed in November after Democrats took control of the House.

Furthermore, Mueller himself is nominally working for the Justice Department, which typically handles congressional requests for testimony through the Office of Legislative Affairs. The head of that office and the deputy attorney general can make decisions on these requests, and the attorney general can also weigh in if the situation warrants it. So Barr could help decide whether or not Mueller agrees to testify if Nadler summons him.

He could try to stop a grand jury from sending materials to Congress

In 1974, the prosecutors and grand jury involved in special prosecutor Leon Jaworski’s investigation into Watergate assembled evidence into a summary report that they called a “road map” and sent it to the House of Representatives. The grand jury wrote that “the evidence referred to above [should] be transmitted forthwith to the House Judiciary Committee for such use as it considers appropriate.” It ended up aiding in the deliberations over the potential impeachment of President Richard Nixon.

In that case, the attorney general wasn’t involved in the road map or its transmission to Congress. Some of Nixon’s White House aides tried to intervene, but were rebuffed in court and some observers have suggested this might be a way around Trump administration efforts to quash the report.

But this time might be different. “Hypothetically, if Mueller’s grand jury wants to write a similar road map, Barr could try to intervene,” says Richard Ben-Veniste, who was a special prosecutor during Watergate. “It would be complicated by the restrictions that are set out in Bob Mueller’s appointment that suggest the attorney general must review the material,” which Barr could try to assert.

But, Ben-Veniste notes, based on the decisions about the Watergate road map, the rights of the grand jury and the role of the chief judge, it’s uncertain that Barr would prevail. “The grand jury’s rights are important and independent of the restrictions on Mueller,” he says. And it’s not clear that Mueller’s grand jury would try to go this route in the first place.

-With Alana Abramson in Washington

Write to Tessa Berenson at tessa.berenson@time.com.