(CNN) Sought-after parts of the Mueller investigation may be made public this week, thanks to a federal judge who's taken an unusual approach in former Trump national security adviser Michael Flynn's case .

Taken together, the judge's orders look like a shortcut to transparency in a moment of executive branch stonewalling.

Each of the documents, once made public, could bring revelations about Mueller's work. The transcripts alone could answer lingering questions about what exactly Flynn said to the Russians that caused so much concern among US intelligence and how a message that factored into the obstruction of justice probe into President Donald Trump played out.

So far, the Justice Department hasn't pushed back on the judge's demands. But it could before the May 31 deadline.

Outside of the Flynn case, the Justice Department is fighting on several fronts to hold back the redacted portions of the Mueller report from the public.

It's not clear at this time how many redactions in the Mueller report that aren't protected by grand jury secrecy relate to Flynn's case. It appears to be very few based on how Mueller structured the report.

What's in the documents

The conversations between Flynn and Kislyak during the presidential transition have only been summarized in court papers and the Mueller report so far. Transcripts of them, which may still be classified, could flesh out the public's knowledge of a major event that Mueller investigated.

The calls between Flynn and the ambassador, in which they discussed Russian reaction to US sanctions and an upcoming United Nations vote about Israeli settlements, led to Flynn lying to the FBI . The calls also set in motion some of Trump's potentially obstructive acts, including his request of then-FBI Director James Comey to let Flynn go.

The other transcript Sullivan demanded, apparently of a voicemail from Trump's personal attorney to Flynn's lawyer as he neared his December 2017 plea deal, is excerpted in the Mueller report but hasn't been published in full.

Mueller instead used ample ellipses to quote from it.

"[I]t wouldn't surprise me if you've gone on to make a deal with ... the government. ... [I]f ... there's information that implicates the President, then we've got a national security issue, . . . so, you know, . . . we need some kind of heads up," Mueller quoted from the transcript in his report.

In theory, the transcripts may have come out in court if Flynn had fought his criminal charge from Mueller to a trial. But his plea agreement stopped the evidence from being aired.

The redacted parts of the Mueller report have also been closely guarded.

Another federal judge in Washington, Amy Berman Jackson, has already received an unredacted copy of the Mueller report so she can weigh it in Roger Stone's criminal case , after his team asked to view it to prepare for his trial. It is not available to the public nor to Stone and his legal team at this time.

And the Justice Department has agreed to let the House and Senate Intelligence committees look at redacted parts of the report on Russian interference as early as this week , under conditions that it must be kept secret. Even with that plan, the committees wouldn't get to see secret grand jury information cited in the report, or redacted parts of the obstruction investigation summary.

Separately, BuzzFeed News and the transparency-oriented Electronic Privacy Information Center have sued over the redactions but won't have a court hearing in their case until July.

Even the Washington Post, which had sued for other sealed filings in the Flynn case, hadn't asked for the transcripts or the unredacted Mueller report sections pertaining to Flynn. They didn't have the ability to ask the court for those particular documents because the documents don't appear to be in the court record.

So without prompting, Judge Sullivan went there. There's also no suggestion that he's already seen the documents he's requested or has them under seal in the Flynn case file already, as is sometimes the case.

"He's certainly familiar with going rogue," said Brad Moss, a Washington-based lawyer who frequently sues the government for public access to documents. Because Sullivan can be so unpredictable for the attorneys practicing in front of him, "it's not necessarily surprising," Moss said. "It's certainly something I wish we saw more from judges."

A no-nonsense judge

Sullivan has cultivated a no-nonsense and sometimes unpredictable reputation. First appointed to a judgeship by President Ronald Reagan, Sullivan was elevated to the DC District Court, the trial-level federal court handling cases in Washington, DC, by President Bill Clinton.

Since then, he's handled several public records transparency cases and many more cases of public interest. That includes the corruption case against the late Sen. Ted Stevens, whose conviction Sullivan set aside following allegations of misconduct by prosecutors.

More recently, he dealt losses to the President in a lawsuit brought by congressional Democrats over Trump's business proceeds. The Justice Department is attempting to appeal.

In overseeing the Flynn case, Sullivan has already made clear he won't tolerate shenanigans.

Previously, he had set Flynn's sentencing for December, and brought the former national security adviser in for what was set to be his final appearance before a judge. But because of an argument from Flynn's defense team about how his case differed from others who pleaded guilty in the Mueller investigation, Sullivan questioned Flynn's sincerity. The proceeding went from a standard judge-defendant hearing, to one where Sullivan asked if Flynn could be prosecuted for treason. (Mueller's team told Sullivan no.)

Sullivan was so harsh at the hearing that Flynn's team asked the judge to postpone giving a sentence. Flynn had been seeking no jail time, and the special counsel's office said that would be appropriate because of his cooperation.

"I am not hiding my disgust, my disdain for your criminal offense," Sullivan said during the sentencing hearing , strongly suggesting he was considering jail time for Flynn. He also commented during the Flynn hearing his disagreement with the probation-only sentence given to Gen. David Petraeus by another judge for sharing classified information.

At the end of the hearing, he told both Mueller's team and Flynn's he still had questions about the case, such as how Flynn's lies impacted Mueller's work.

The sentencing hasn't been rescheduled yet.

"We saw a judge in Sullivan who was prepared to sentence Flynn to jail. He's trying to make an evaluation of whether this guy is a traitor, not in a legal sense, but behaved with bad purpose and judgment," said Michael Zeldin, a former federal prosecutor who is now a CNN legal analyst.

While he's still handling Flynn, Sullivan appears to be using his authority to wedge open more public access to that part of the investigation.

He's already ordered the Justice Department to put the redacted version of the Mueller report previously released on the agency's website into the court record, which is available online.

But on May 17, when prosecutors tried to do this, the file was too big. Their backup plan was to hand-deliver a printed copy to Sullivan's chambers instead.

That wouldn't do for Sullivan. He ordered the Justice Department to break it into pieces and still file the 448-page document publicly in the court record.