WASHINGTON (Reuters) - The U.S. Justice Department on Thursday fought in federal court to keep some minor details of its counterintelligence probe into Russian interference in the 2016 election under wraps, even after President Donald Trump had unwrapped them.

FILE PHOTO: Voters cast their votes during the U.S. presidential election in Medina, Ohio, U.S. November 8, 2016. REUTERS/Aaron Josefczyk/File Photo

Earlier this month, Trump declassified a Republican memo which alleges that the FBI used a dossier prepared by a former British intelligence officer to authorize surveillance on a Trump campaign adviser suspected of being a Russian agent.

Despite that unprecedented public disclosure, a Justice Department lawyer told a judge in oral arguments at the U.S. District Court for the District of Columbia on Thursday that the government still cannot reveal the date when it received a complete copy of the dossier for fear it might “confirm previously unconfirmed facts about a law enforcement-sensitive” investigation.

That argument exasperated U.S. District Court Judge Amit Mehta, who said that Trump has since changed the landscape for what can be disclosed by declassifying details of a counterintelligence investigation.

“That’s going to be a hard sell, given what the president’s done,” Mehta said. “He has now declassified an entire national security investigation.”

Mehta said that normally the Justice Department’s objections to providing such information in private litigation would be justified. But, “this isn’t the ordinary case,” he said.

He suggested the department consider whether it can submit a one-sentence page disclosing when it received the dossier.

The Justice Department was in court on Thursday trying to beat back a subpoena from the news organization BuzzFeed.

In early 2017, Buzzfeed published a copy of the dossier, penned by Christopher Steele and funded in part by U.S. Democrats.

The dossier makes some serious and salacious allegations against Trump, and suggests that the Russians and Trump’s campaign colluded ahead of the 2016 election. Trump has denied colluding with Russia. U.S. intelligence agencies have concluded Russia interfered in the 2016 presidential campaign, though Russia has denied it.

Buzzfeed is seeking material from the Justice Department to help defend itself against a defamation lawsuit it is facing by a Russian businessman who claims he was libeled in the dossier.

Much of the information it sought previously it no longer needs because it was disclosed elsewhere, a lawyer for the company conceded on Thursday. But the company still contends it needs to know the time frame for when the FBI obtained the dossier.

The dossier has prompted a backlash by Congressional Republicans, who allege the FBI used it to improperly obtain a warrant from a U.S. Foreign Intelligence Surveillance Court without verifying the facts or disclosing it was funded by Democrats.