LONDON (AFP) - Lawyers for a man who helped publish Edward Snowden's leaked files asked Britain's High Court on Thursday to prevent the copying of data seized during his detention at a London airport.
Mr David Miranda, 28, the partner and assistant of Guardian journalist Glenn Greenwald, was on Sunday detained for nine hours at Heathrow Airport under anti-terror laws and had his laptop, phone and other electronic equipment confiscated.
The High Court in London heard his legal team's application for an injunction preventing the authorities using, copying or sharing data from the seized devices.
The Brazilian's lawyers want the injunction to run "until the legality of that seizure has been determined by this court".
Mr Miranda's lawyer Matthew Ryder told two judges it had been necessary to go to court because Britain's interior minister and police chief had both refused to give undertakings "protecting the confidentiality of sensitive journalistic material".
"Those undertakings have not been agreed and that is why we are here now," he said.
Mr Miranda, who helped Mr Greenwald work on the Snowden material, has launched an application for a judicial review, arguing that his detention while transiting through Heathrow was a misuse of anti-terrorism legislation and breached his human rights.
Snowden, a former US National Security Agency contractor, has been granted temporary asylum in Russia as he flees a US bid to prosecute him for leaking information on mass surveillance programmes conducted by the NSA and Britain's electronic eavesdropping agency GCHQ (Government Communications Headquarters).
Based on the material Snowden provided, the Guardian has published a series of reports detailing the programmes, infuriating Washington.
The Guardian reported that Mr Miranda's lawyers claim in their submission that he was "subjected to intensive, wide-ranging and intrusive questioning... but he was not asked, nor was it suggested, that he was involved with terrorist groups, organisations or terrorist activity."
The left-liberal newspaper's editor Alan Rusbridger has claimed he was ordered to destroy some of their classified Snowden files during a shadowy visit from a senior government official a month ago.
The government confirmed on Wednesday that the official sent to the Guardian was Cabinet Secretary Jeremy Heywood, the top civil servant who is Prime Minister David Cameron's most senior policy advisor.
Mr Cameron has faced calls to address parliament on the matter.
Mr Keith Vaz, chairman of the British parliament's Home Affairs Select Committee scrutiny body, on Wednesday called on Mr Cameron to address the House of Commons when it returns from recess in September.
"The actions of the cabinet secretary are unprecedented and show that this issue has reached the highest levels of government," he said.
"The prime minister must make a full statement to parliament on the day it returns."
A spokesman for Cameron's deputy Nick Clegg said that asking The Guardian to comply was better than taking legal action over the documents leaked by Snowden.
Guardian editor Rusbridger said two GCHQ security experts oversaw the destruction of hard drives on July 20.
A senior editor and a Guardian computer expert used power tools to wreck the hard drives and memory chips.
Beforehand, Mr Rusbridger had informed government officials that copies of the encrypted files existed outside Britain and that the newspaper was not their sole recipient.
A Downing Street spokesman told AFP: "We won't go into specific cases, but if highly sensitive information was being held unsecurely, the government would have a responsibility to secure it."
The hard drive destruction and Mr Miranda's detention have triggered unease in several countries.
Russia condemned the "perverse practice of double standards applied by London in the field of human rights".
The Council of Europe, a pan-European rights body that is separate from the European Union, meanwhile wrote to the British government questioning whether the moves were compatible with its obligations under the European Convention on Human Rights.
EU Justice Commissioner Viviane Reding said she fully shared those concerns.
Germany's top human rights official expressed "great concern" about media freedom in Britain, and branded Mr Miranda's detention "unacceptable".