The ruling from US District Judge Colleen Kollar-Kotelly does not preclude the DoJ from trying again to indict Comey, but it does suggest prosecutors may have to do so without citing communications between the former FBI chief and a close friend, Columbia University law professor Daniel Richman.
Comey was charged in September with lying to Congress when he denied having authorised an associate to serve as an anonymous source for media coverage about the FBI.
In pursuing the case, prosecutors cited messages between Comey and Richman that they said showed Comey approving of Richman interacting with journalists for certain FBI-related coverage.
The case was dismissed last month after a different federal judge ruled the prosecutor who filed the charges, Lindsey Halligan, was unlawfully appointed by the Trump administration.
But that ruling left open the possibility that the US government could try again to seek charges against Comey, a long-time foe of President Donald Trump.
Comey has pleaded not guilty, denied having made a false statement and accused the DoJ of a vindictive prosecution.
After the case was thrown out, lawyers for Richman sought a court order to bar prosecutors from continued access to his computer files, which the DoJ obtained through search warrants in 2019 and 2020 as part of a media leak investigation that was later closed without charges.
Officials searched the files for communications between Comey and Richman they could use to build the case against Comey. But Richman and his lawyers say prosecutors exceeded the scope of the warrants, illegally held onto communications they should have destroyed or returned, and conducted new, warrantless searches of the data.
Kollar-Kotelly granted Richman's request for a temporary restraining order, instructing the DoJ "not to access the covered materials once they are identified, segregated, and secured, or to share, disseminate, or disclose the covered materials to any person, without first seeking and obtaining leave of this court."
She gave the DoJ until Monday to certify that it is in compliance with the order.
Kollar-Kotelly said her order would remain in effect through to Friday, "or until dissolved by further order of this court, whichever comes first."
A DoJ spokesperson declined to comment on the ruling.
