Principal District and Sessions Judge CS Murugan remanded R Kalai Lingam, R Thiruselvan, M Tamilarasan and Kaviarasu when they were presented before the court by a team of the National Investigation Agency.
The accused, who were arrested last month, hail from Sivaganga district in Tamil Nadu.
The NIA, which launched a probe into the case, formally arrested the four activists and brought them to Puducherry for detailed interrogations.