Lawyers acting for the partner of a journalist held for nine hours under anti-terror laws will take his case to the High Court today.
They have applied for an injunction preventing the police or government using, copying and sharing data from electronic devices seized from David Miranda during his detention.
Two judges will also hear their argument that Mr Miranda's detention at Heathrow Airport was a misuse of Schedule 7 of the Terrorism Act 2000 and breached his human rights.
The Brazilian is the partner of Guardian journalist Glenn Greenwald who has worked with US whistleblower Edward Snowden on a series of security services exposes.
He was held without charge for the maximum time permitted under the anti-terror legislation as he changed planes on a journey from Berlin to his home in Brazil.
Scotland Yard says the detention was "legally and procedurally sound" but that is disputed by Mr Miranda's lawyers and has been questioned by a former Lord Chancellor.
Lord Falconer, who helped introduce the law, insisted the powers were designed to be used against those suspected to be terrorists.
But Home Secretary Theresa May said the police were right to act if they believed Mr Miranda was in possession of material - that he was carrying for Mr Greenwald - that could be useful to terrorists.
"If the police believe someone has in their possession highly sensitive stolen information that could help terrorists that could lead to a loss of life, it is right the police should act," she said.
"I believe schedule 7 of this act enables police to do that."
The Guardian said the injunction would seek to prevent the use of data taken from the laptop, phone and other electronic equipment confiscated from Mr Miranda at the airport.
Gwendolen Morgan, of Bindman Partners, told the newspaper the legal action had been taken because the authorities had failed to give sufficient guarantees.
Lawyers are expected to argue that the police exceeded their powers by detaining a transit passenger who had not formally entered the UK.
They say in their submission that Mr Miranda 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 newspaper reported.
He was warned that a failure to co-operate could result in him being jailed.
The case is already being looked into by David Anderson, the independent reviewer of anti-terror laws.
Downing Street was aware of the planned detention but insists there was no political involvement in the decision - which was also communicated to the White House.
A poll found that while most voters (66%) backed the need for the powers used to detain Mr Miranda, only 37% thought it was right to use them on the grounds he might have data useful to terrorists.
The survey by YouGov showed the public thought it unreasonable to threaten him with jail for not disclosing passwords, by 47% to 38%, and half said his computer and phone should have been handed back when he was released.