The Supreme Court said it will allow an unnamed foreign government-owned company to file a sealed appeal related to special counsel Robert Mueller’s investigation.

Lower courts ruled that the company must turn over information and comply with a grand jury subpoena issued in Washington.

Earlier this month, the Supreme Court denied an emergency request that would have frozen the financial fee the company incurs every day it doesn’t comply with the subpoena.

The Supreme Court had not considered the merits of the appeal, which has yet to be filed. When it is filed, it will be under seal — though there will be a redacted version for the public to view.

The U.S. Court of Appeals for the District of Columbia Circuit in December ruled that the company was exempt to the Foreign Sovereign Immunities Act, and had to comply with the grand jury subpoena.

It is not known whether Mueller is the one who actually issued the subpoena, though CNN reported earlier this month that one of the firms involved is Alston & Bird — a firm that has previously represented a Russian oligarch and a contractor for the Russian government.

The extremely secretive case has become a focal point for those watching Mueller’s investigation into Russian election interference and possible connections to the Trump campaign.

The high court has never before heard a case where all parties and arguments stayed under seal.