David Correia, a Florida businessman, was arrested on Wednesday at John F Kennedy International Airport in New York, after flying there to turn himself in on charges related to a scheme to funnel money from international sources to a Republican congressman and a political action committee supporting Mr Trump.
Mr Giuliani is the president's personal lawyer, and has been representing him on issues related to the ongoing impeachment investigation in the House of Representatives. He has said he had no knowledge of illegal donations.
Mr Correia has been accused of conspiring with other defendants — Mr Giuliani's associates Lev Parnas and Igor Fruman — to donate money to make political donations as they attempted to set up recreational marijuana businesses in the US.
Mr Parnas and Mr Fruman were arrested last week at Washington's Dulles International Airport with one-way international tickets. A fourth defendant, Andrey Kukushkin, was arrested prior to that in San Francisco.
Court documents allege that a scheme to funnel money to Republican former congressman Pete Sessions, state Republicans and a political action committee supporting Mr Trump began in 2018, when Mr Parnas and Mr Fruman began making “substantial contributions” with the aim of “enhancing their influence in political circles and gaining access to politicians”.
To do so, the two used wire transfers from a corporate entity – Global Energy Producers (GEP) – that they had created in order to hide their tracks, including a $325,000 (£261,000) donation to the America First Action committee, a super PAC that supports Mr Trump. In addition to supporting the president, that super PAC spent heavily during the 2018 election to prop up Mr Sessions, who had posed with Mr Parnas and Mr Fruman just days before he sent a letter to secretary of state Mike Pompeo, questioning the fitness of US ambassador to Ukraine Marie Yovanovitch.
Ms Yovanovitch, who is no longer serving as an ambassador to Ukraine, has now alleged she was targeted by a campaign to remove her by Mr Giuliani and others. Mr Trump later badmouthed Ms Yovanovitch during a 25 July call with the president of Ukraine, Volodymyr Zelensky, notorious now for him asking for an investigation into the Biden family. The former ambassador had served under presidents from both parties, and was thought to have been a hindrance to efforts to corrupt Ukrainian politics.
“Campaign finance laws exist for a reason. The American people expect and deserve an election process that has not been corrupted by the influence of foreign interest, and the public has a right to know the true source of campaign contributions,” William Sweeney Jr, the assistant director in charge of the US office, said during a press conference on Thursday.