At a press conference in the Swiss city on Monday, Baltasar Garzón, who heads the legal team working for Wikileaks founder Julian Assange, accused the American internet search engine of an "attack on journalism" by providing the emails of three Wikileaks journalists to the U.S law enforcement agency.
He told the Geneva Press Club that the staff members had only been informed in December that the contents of the accounts had been handed over to federal investigators two and a half years ago.
The former judge, who once attempted to extradite General Pinochet from Britain to stand trial for abuse of power and who launched a failed bid to investigate the Franco-era crimes in Spain, said the constitutional rights of those Wikileaks journalists had been breached.
Google provided the data in response to a warrant by the FBI.
"This action is illegal and unacceptable," Garzón charged, adding that it was an "attack on journalism and journalists, especially those working on security issues".
Wikileaks is arguing that the warrant could have been challenged had the Wikileaks employees been informed of the request at the time.
Garzón also took the opportunity to slam the treatment of Wikileaks founder Assange, who has been holed up in the Ecuadorian embassy in London since 2012, after losing an appeal against extradition to Sweden to face rape allegations.
"It is outrageous that in the 21st century fundamental rights such as the right to political asylum are not being observed," said Garzón, adding that Assange cannot even step outside for fear of being arrested.