Observers are buzzing about a series of events in the last 60 days in the case of Michael Flynn, the Trump national security adviser who on Dec. 1 pleaded guilty to one count of lying to the FBI in the Trump-Russia investigation. The new developments might add up to very little or they might be significant. In any event, they are raising eyebrows.

First, there is some mystery surrounding the removal of Judge Rudolph Contreras from the case. Just days after accepting Flynn's guilty plea, Contreras was taken off the case by the U.S. District Court for the District of Columbia. No reason was given.

Of potentially more interest is Contreras' replacement, Judge Emmet Sullivan. Sullivan is well known in legal circles for having been the judge in the case of Ted Stevens, the Republican senator from Alaska who was prosecuted for corruption by the George W. Bush Justice Department. Stevens was convicted in October 2008, causing him to lose his bid for re-election the next month. But it later came to light that the Justice Department had improperly withheld exculpatory evidence. In April 2009, Eric Holder, the Obama attorney general who inherited the mess, dropped the case.

What Flynn watchers are noting today is that when all that happened back in 2009, Sullivan ripped into the Stevens prosecutors with an anger rarely seen on the bench. Sullivan was furious that the federal government had repeatedly withheld evidence from the Stevens defense and has been known ever since as a judge who is a stickler for making sure defendants are allowed access to all the evidence they are entitled to.

On Dec. 12, after just a few days on the Flynn case, Sullivan, acting on his own, ordered the office of special counsel Robert Mueller "to produce to [Flynn] in a timely manner — including during plea negotiations — any evidence in its possession that is favorable to defendant and material either to defendant's guilt or punishment."

Sullivan also ordered Mueller "to produce all discoverable evidence in a readily usable form." And he declared that "if the government has identified any information which is favorable to the defendant but which the government believes not to be material, the government shall submit such information to the Court for in camera review." In other words, Sullivan declared that he, not Mueller, would be the judge of what evidence should be produced.

While the move could be simply standard procedure for Sullivan, it was nevertheless notable because Flynn had already pleaded guilty, and, as part of that guilty plea, agreed to "forgo the right to any further discovery or disclosures of information not already provided at the time of the entry of [Flynn's] guilty plea."

"It certainly appears that Sullivan's order supersedes the plea agreement and imposes on the special counsel the obligation to reveal any and all evidence suggesting that Flynn is innocent of the charge to which he has admitted guilt," wrote National Review's Andrew McCarthy, a former federal prosecutor.

On Jan. 31, the two sides in the case agreed to delay sentencing for Flynn until at least May. Some observers saw that as an entirely routine development in a case in which the defendant is cooperating with prosecutors on an open matter. On the other hand, in the Flynn case, the delay took place in the context of Sullivan's evidence order, and there is no way for the public to know whether that played a role in the decision.

Fast forward to Wednesday. Prosecutors and the defense submitted to Sullivan a proposed order limiting the use of any new evidence produced by the government. The evidence can be used by Flynn's defense "solely in connection with the defense of this case, and for no other purpose, and in connection with no other proceeding." The proposed order, awaiting Sullivan's approval, also set out rules for handling "sensitive" materials.

That's where things stand now. The latest filings indicate both sides are taking Sullivan's order seriously, which is certainly a good idea, given Sullivan's history. But is there actually not-yet-produced evidence that might help Flynn? If so, would it have any effect on the case in which Flynn has already pleaded guilty? And would it have any effect on the larger Trump-Russia investigation? There are no answers right now, but United States v. Michael Flynn remains a case to watch.