Lawyers for David Miranda, the partner of Guardian reporter Glenn Greenwald, said the seized items contain confidential information and asked the High Court to prevent the government from "inspecting, copying or sharing" the data. British officials took computers, memory sticks and other electronic items from Miranda when he was detained and questioned for nine hours at London's Heathrow Airport under Schedule 7 of the country's Terrorism Act.
"Confidentiality, once lost, can clearly never be restored," Lawyer Gwendolen Morgan said in a statement. "If interim relief is not granted, then the claimant is likely to suffer irremediable prejudice, as are the other journalistic sources whose confidential information is contained in the material seized."
London police have argued that Miranda's detention was "legally and procedurally sound." Home Secretary Theresa May has defended the police, saying they were right to act if they "believe someone has in their possession highly sensitive stolen information that could help terrorists, that could lead to a loss of life."
Greenwald has written about NSA programs in the United States using files disclosed by Snowden, who now has temporary asylum in Russia. The Obama administration wants Snowden to face trial in the United States for the leaks.
The 28-year-old Miranda was returning home to Brazil from Germany, where he had met with Laura Poitras, a U.S. filmmaker who has worked with Greenwald on the NSA story.