The Supreme Court on Monday said it would not take up a case brought by an unknown, foreign-owned company challenging a subpoena in special counsel Robert Mueller’s investigation.

In its order denying the mystery corporation’s opinion, the Supreme Court also allowed for certain briefings in the highly secretive case to be filed under seal.

The company has lost its challenge multiple times at the lower courts. It is facing steep fines — $50,000 a day — for continuing to resist the request that it produce certain documents. The Supreme Court previously declined to halt the lower court’s order imposing the fines.

The company has argued its compliance with the grand jury subpoena would violate the Foreign Sovereign Immunities Act. Lower courts have ruled that even if the law provided the corporation immunity, the subpoena matter fit within an exception in the law for commercial activities.

The Supreme Court’s move comes as Mueller’s investigation winds down with his submission of his report to Attorney General Bill Barr on Friday. However, a lawyer in a separate case challenging a Mueller subpoena has said that investigators are still seeking the testimony of his client, Andrew Miller, an associate of Roger Stone. The lawyer, Paul Kamenar noted that Stone’s case is also being handled by the local U.S. attorney’s office.

The foreign-own company first received the subpoena in July 2018, and took Mueller to court over the request the following month. However, the case’s early proceedings took place under extreme secrecy and the existence of the case — and its possible link to the Russia probe — only became publicly known in fall 2018.

Since then some of the court documents have been posted publicly, in part due to litigation brought by a press freedom organization, shedding limited light onto details of the case.