A company owned by a foreign government which appears to be locked in a fierce battle with Special Counsel Robert Mueller has taken their case to the Supreme Court, according to a new legal filing presented Saturday to Chief Justice John Roberts.

The unidentified firm has asked the Supreme Court to block Mueller from obtaining records through a subpoena after a federal appeals court turned down the company's effort to block the court ordered release of documents.

The identity of the firm and the foreign country at issue remain closely guarded secrets, but POLITICO first reported earlier this year that the dispute appeared to involve Mueller’s prosecutors. A POLITICO reporter was in the D.C. Circuit Court of Appeals clerk’s office in October when a person connected to the appeal arrived to request a copy of the special counsel’s latest filing in the case. When the case was argued at the D.C. Circuit last week, the courtroom was closed to the public. Court personnel went to unusual lengths to preserve the secrecy, ordering journalists to leave the floor where lawyers were presenting their positions. -Politico

The court's public docket has offered few clues - containing no information on the parties or their attorneys. Tuesday, however, a three-page order revealed that the witness fighting the subpoena is a corporation owned by a foreign state.

The firm's argument that its status as an extension of a foreign government made it immune from subpoenas was rejected by a three-judge DC Circuit panel, while the judges were also unpersuaded by the state-owned company's claims that complying with the subpoena would violate laws in their home country.

After the order was filed Tuesday, sealed filings continued in the appeals court in what appeared to be a bid to stay the D.C. Circuit’s ruling or appeal it further. On Friday, the appeals court denied a motion from the company. The precise nature of the motion was not disclosed. -Politico

The Supreme Court's online docket only reveals the request for a stay of the subpoena, and the fact that the company has asked to proceed under seal.