The Federal High Court has granted the State Security Service an approval to keep Omoyele Sowore in custody for initial 45 days.
Taiwo Taiwo of the Abuja Division also said the SSS would get additional permission to keep locking Mr Sowore up for his activism.
Mr Sowore had called for a good governance revolution in Nigeria last week, drawing immediate fears from President Muhammadu Buhari and other elements in his government.
Mr Sowore was arrested in Lagos on August 3 by SSS operatives who stormed his apartment.
The arrest came two days before the nationwide protest was scheduled to take place on August 5 across the country.
After keeping Mr Sowore in custody for more than 48 hours in violation of the law, the SSS asked a federal judge for permission to further incarcerate him and was granted on Thursday morning.
Source: Premium Times