Lawyers representing a solicitor held by police are to seek a judicial review of the circumstances of his arrest.
Mr Sandhu is a solicitor based in Limavady
Limavady solicitor Manmohan Sandhu was arrested on Tuesday and is being held in Antrim police station over allegations of serious crime.
His lawyers claim police secretly taped conversations between him and clients.
The High Court will be asked to look at the legality of the bugging devices allegedly used to record confidential conversations at Antrim police station.
Detectives on Thursday successfully applied for another 48 hours to interview Mr Sandhu. The extension runs out at 1000 GMT on Saturday.
It is understood police will seek another extension at the High Court. This is likely to happen after the judicial hearing.
The Law Society, the body which represents the legal profession, is to take the case up with the chief constable.
Law Society chief executive John Bailie is to meet Hugh Orde in Belfast on Monday.
Mr Bailie said that the allegations of covert taping by police represented an "intrusion into the solicitor-client relationship".
"A client in these circumstances - who is arrested and in police custody, suspected of having committed a criminal offence - needs to be able to speak to his solicitor candidly," he said.
"The administration of justice requires that should happen: he needs to be guaranteed that it is kept confidential.
"I think also the reason why we are taking this so seriously is that it is the first occasion of which I am aware in Northern Ireland that there has been this kind of intrusion into the solicitor-client relationship."
Mr Sandhu's solicitor, Joe Rice, wrote to the Law Society to complain about how, he claims, the police gathered evidence by covertly taping confidential conversations.
Mr Rice alleges the conversations, allegedly taped at Antrim police station, led to Mr Sandhu being questioned about serious terrorist activity including membership of a loyalist paramilitary organisation.
The letter from Mr Rice to the Law Society's chief executive also said: "It is a sad day for our criminal justice process that a solicitor cannot guarantee that his advices to his client in a police station may not be free from state interference."
He also stated: "I am sure you will share my concern that the right to confidentiality that must exist between solicitor and client has now been eradicated.
"This is a deliberate move by the authorities and no solicitor can at present guarantee his client that any pre-interview or indeed post-interview consultations at police stations in Northern Ireland are private and confidential."
Police refused to confirm or deny the identity of Mr Sandhu, but confirmed on Thursday they have been granted another 48 hours to question a man at Antrim police station.