This article was produced in partnership with the Pulitzer Center on Crisis Reporting.

GUANTÁNAMO BAY, Cuba — Something secret was supposed to start on Saturday related to the case of a Malaysian prisoner who has been held as a terror suspect for 13 years at Guantánamo Bay.

Then a federal judge put a stop to it following a classified hearing. The judge did not say what it was or why he had blocked it, other than to note that he was making his order public so that the people involved did not arrive for the secret proceeding only to find that it had been canceled.

“The defendants are restrained from conducting the two proceedings that are scheduled to commence on September 28, 2019 in a certain location,” Judge John D. Bates of the U.S. District Court in Washington, D.C., wrote in an order dated last Friday but released this week. “We are issuing this order today as a courtesy to petitioner and defendants as it may affect their travel or logistical arrangements.”

Judge Bates’s reasoning for issuing the order is classified, as were all the associated filings, including an emergency habeas corpus petition filed by military and civilian lawyers for the defendant, Mohammed Nazir Bin Lep.