Eggs were thrown at Gazi Salauddin Tanvir outside the Bogura Chief Judicial Magistrate Court on 5 August as he was being taken toward jail.
The incident followed a court order sending Tanvir to jail after a hearing in a Cyber Security Act case.
Detective police arrested him at a residential building in Dhaka's Monipuri area earlier that morning and brought him to Bogura for the hearing.
The case concerns allegations that a Facebook account linked to Tanvir carried objectionable comments about the prime minister.
The case complaint alleges that the post was made on 29 July, was later deleted, and led to a case filed at Bogura Sadar police station on 2 August.
Accounts differ on who threw the eggs: one identifies Chhatra Dal activists, while another says some people present threw them during a protest by Chhatra Dal activists.
The protesters chanted slogans as Tanvir was removed from the court area.
Rafiul Islam, the member secretary of the Government Azizul Haque College Chhatra Dal unit, called for exemplary punishment over the alleged comments.
Bogura detective police officer Iqbal Bahar said police would seek remand to question the accused.
Iqbal Bahar said police controlled the court-premises situation and that no major untoward incident occurred.