The Supreme Court ruled Tuesday a mysterious company tied up in special counsel Robert Mueller’s Russia investigation must comply with a subpoena or continue paying a daily fine.

According to Politico, the decision will force the company — which has only been described as a corporation owned by a foreign government — to follow the subpoena first issued to it last fall.

Chief Justice John Roberts referred the case to the full court, Politico noted, one month after he issued a stay on the fines being levied on the corporation.

The case has been shrouded in secrecy. An entire floor of a Washington, D.C. courtroom was sealed off last month as lawyers for each side argued in front of a judge. The identity of the witness has yet to be revealed.

Early rumors suggested the witness might have been President Donald Trump, but that was debunked by Trump lawyer Jay Sekulow.

Mueller’s probe began in May 2017 over allegations the Trump campaign might have colluded with Russia to defeat Democrat Hillary Clinton in the 2016 election. No such evidence has been made public, but the investigation is ongoing and many details remain secret.

None of the Supreme Court justices issued a public dissent on the Tuesday ruling, which could indicate the court wants to stay out of the Russia matter.

“The fact that no justice publicly noted a dissent from today’s order suggests that the court is inclined to stay out of this dispute altogether,” University of Texas law professor Stephen Vladeck told CNN.

The unnamed corporation filed a motion on Monday that asked for a judicial review of the case.