A prisoner at Wheatfield Prison in Dublin is challenging his segregation from other inmates following the use of a remote control helicopter to bring drugs into the prison.
The remote control drone carrying drugs crash landed into an exercise yard within the prison in west Dublin on 24 June.
Mr Justice Daniel Herbert said it was clear from the intelligence received by prison authorities and CCTV footage that the inmate was "knee deep in the plot".
Barrister Owen Lawlor said the governor's decision to keep his client in solitary confinement is irrational and unreasonable because there is no evidence of a fresh plot to bring drugs into the prison.
Mr Lawlor said the governor may have concluded that his client was involved in the "airborne plot" but there is no reason to conclude he will do it again.
Mr Lawlor said the decision to keep him segregated should be overturned by the High Court.
He applied for leave to take a judicial review of the governor’s decision, which the High Court has granted.