Robert Mueller is fighting a mystery witness in court who is proving to be a major nemesis.

A case has been going back and forth between the D.C. District Court and the Circuit Court of Appeals since August, and it concerns a major hiccup in the Special Counsel’s witch hunt. In fact, some speculate that the case could destroy Mueller’s authority and shut him down for good.

Everything has been under seal since the case started, but there has been plenty of speculation about the nemesis of Robert Mueller and what it concerns.

No one in the media even knows what the issue is, but it seems to involve a grand jury witness.

Whatever the actual dispute is, and whomever the person is, the court will address this issue within the next two weeks.

“The D.C. Circuit announced Friday that they will be hearing oral arguments in the case on December 14, in a closed session.”

The latest development comes a couple weeks after the unknown appellant filed a 6,487-word brief and just days after the FBI illegally raided the home of a Justice Department whistleblower.

Many people wonder if it involves Mueller’s authority or speculate on the actual person behind it, even considering it might be President Trump.

Some snooping by a Politico reporter led to the speculation, but Trump’s lawyer Jay Sekulow denied it.

Attorney Ted Boutrous told Politico that “the most likely scenario is someone filed a motion to quash or otherwise resisted a grand jury subpoena, and the judge issued an order denying that and saying the witness needs to testify.”

“When the case went before the entire D.C. Circuit, the only judge to recuse himself was the lone Trump appointee, Gregory Katsas.”

An attorney for a senior Trump staff member said in October, “It could be anyone who’s been subpoenaed by the special counsel for anything.”

Politico reported, “It’s unclear exactly what the two sides are fighting over, but the case appears to resemble a separate legal battle involving an associate of Trump ally Roger Stone, Andrew Miller, who is fighting a Mueller subpoena.

“Miller’s lawyers are using the case, slated to be argued at the D.C. Circuit Court of Appeals early next month, to mount a broad legal assault on Mueller’s authority as special counsel.”

However, nothing on the two dockets for the mystery grand jury fight mentions Mueller or his team.

“However, a Politico reporter who visited the appeals court clerk’s office on a day when a key filing in the dispute was due earlier this month observed a man request a copy of the special counsel’s latest sealed filing so that the man’s law firm could craft its response.”

“The individual who asked for the secret filing declined to identify himself or his client and replied ‘I’m OK’ when offered a reporter’s business card to remain in touch.”

Basically, he wasn’t saying anything.

“Three hours later, a sealed response in the grand-jury dispute was submitted to the D.C. Circuit.”

Another detail emerged Wednesday strengthening the secret legal battle’s apparent tie to Mueller’s probe.

A spokesman for Mueller’s office, Peter Carr, declined to comment.

“Several other lawyers who represent witnesses in the Mueller investigation also said they were unaware of who’s crossing legal swords with the special counsel’s team in the largely secret case.”

“The bottom line is the most likely scenario is someone filed a motion to quash or otherwise resisted a grand jury subpoena, and the judge issued an order denying that and saying the witness needs to testify,” said Ted Boutrous, a Gibson Dunn & Crutcher lawyer.

“The grand jury cases pose a threat to Mueller’s investigation because they can serve as vehicles to get questions of his authority and legal legitimacy before appellate judges relatively quickly.

“Such questions have also been raised by defendants in some of Mueller’s criminal cases, but all the human defendants who have set foot in a courtroom have ultimately decided to plead guilty and drop any challenges to the special counsel’s authority or tactics.”

One fact remains clear. There will be someone to leak something eventually, and everyone will know who’s fighting Robert Mueller’s outrageous authority in court.