A secret legal dispute over a grand jury subpoena believed to be linked to special counsel Robert Mueller’s investigation has made its way to the Supreme Court, with Chief Justice John Roberts on Sunday night putting on pause a contempt order in the case.

Little is known about the sealed case, beyond that a mystery foreign company has resisted the subpoena and has lost its efforts to quash it at the federal court and appellate court level.

There has been no official confirmation that the subpoena came from Mueller’s probe. However, Politico reported earlier this year signs the case was Mueller related, and there have been other sightings at the federal courthouse in D.C. suggesting Mueller’s team was involved. A sealed hearing in the case in front of an appellate court panel earlier this month prompted an extraordinary amount of secrecy, with reporters being cleared from the entire courthouse floor where the judges were hearing the arguments.

Roberts on Sunday temporarily halted a contempt order the company is facing for resisting the subpoena, including the fines the company is accruing for defying the subpoena. Roberts’ order is public, but it provided no new details about the case. His move came after the company on Saturday requested the stay, in a filing that is noted in the court’s docket but is not available to be read publicly.

Roberts on Sunday ordered briefing on the matter due by noon on Dec. 31. It is possible those filings will be under seal.

Previously, an appellate court panel upheld the subpoena, in a vaguely worded judgement. The court revealed that the case had been brought by an unnamed company, owned by “Country A,” that had claimed that the Foreign Sovereign Immunities Act made the company immune from the subpoena. The appellate court affirmed a district court’s decision that said the matter fell within an exception in the law for commercial activities.

Read the Roberts order below: