Lawyers for Rudy Giuliani accused federal investigators of secretly obtaining access to his online storage account, saying prosecutors were acting as if they were taking down a terrorist or the head of a drug cartel.
Federal authorities are investigating whether Giuliani illegally lobbied the Trump administration in 2019 on behalf of Ukrainian figures.
Last month they seized electronic devices from his Manhattan office in a dawn raid.
Since then, aides close to Trump suggest the former president has been cool on riding to the rescue of his former adviser and lawyer, and is reluctant to issue a statement of support while investigators close in.
Rudy Giuliani's lawyers made their their first filing after the FBI raided his office on April 28, raising concerns about what they called a 'covert warrant' to search his Apple iCloud
In a filing with federal court in Manhattan on Monday, Giuliani's lawyers said investigators carried out a covert search of their client's Apple iCloud account in 2019.
'The validity of the 2019 covert warrant, and the handling of the information obtained by the prosecutor are serious questions that must be resolved before any further damage is done,' said Giuliani's lawyer Robert Costello.
The subject of such warrants is contentious among online privacy campaigners and data storage companies.
The Justice Department allows them only when there is a concern that evidence may be destroyed or witnesses intimidated.
Costello said that meant his client was being treated as if he were the head of a cartel.
'Unfortunately for Giuliani, and even more unfortunately for the attorney-client privilege and executive deliberation privilege, and the public's perception that those privileges are real, the SDNY simply chose to treat a distinguished lawyer as if he was the head of a drug cartel or terrorist, in order to create maximum prejudicial coverage of both Giuliani, and his most well-known client – the former President of the United States,' he wrote.
The letter was Giuliani’s first legal response to the raid.
Federal prosecutors want to appoint a 'special master' who will review the evidence for anything covered by attorney-client privilege.
The warrants are part of a probe into whether Giuliani's work on Ukraine violated lobbying laws.
Giuliani aides want Donald Trump (pictured recently playing golf in West Palm Beach, Florida) to issue a statement saying the lawyer was carrying out his instructions in Ukraine and so was not part of a foreign lobbying operation
He was instrumental in the firing of the U.S. ambassador to Ukraine as he went about looking for political dirt on Joe Biden ahead of last year's election.
No charges have been brought against him although two of his associates, Lev Parnas and Igor Fruman, are awaiting trial for their alleged role in the effort.
The Daily Beast reported that Giuliani's associates are increasingly anxious that Trump issue a statement saying that his lawyer was working on the president's behalf, rather than an illegal foreign influence operation
'It's a question now of whether or not [the former president and his team] want to leave Rudy to fend for himself or if they're going to take a stand against this,' a person close to Giuliani said.
'Right now, we don't know.'
But Trump's advisers have reportedly told him to stay away, for fear that any public declaration could rebound on him.
The former president has told associates that he did not always know what his personal lawyer was doing.