Samajwadi Party leader Abu Asim Azmi was taken into police custody on Tuesday while he was on his way to participate in a party rally in Shivaji Park in Mumbai.
Azmi, a Rajya Sabha member, was taken to a police station in South Mumbai at around 1 pm, police said.
Authorites had denied permission for the rally, after which the Samajwadi Party moved the court on Monday.