They were protesting against Vala's decision to invite the BJP to form the government in Karnataka despite the saffron party's numbers being less than the combined tally of the Congress and the Janata Dal (Secular) in the state Assembly.
Congress city unit chief Mahesh Rajput, who led the protest outside Vala's Nutan Nagar society residence near Kalavad Road here, called the Karnataka governor's act a "blot on democracy"
"Despite being the governor of a state, Vala has acted like a BJP worker," Rajput alleged.
Deputy Commissioner of Police Harshad Mehta said, "We have detained 30 Congress workers from outside the residence of the Karnataka governor. No member of Vala's family was at home when the protest and sloganeering took place."
Protests by the Congress against Vala's decision were also held at Ahmedabad and Vadodara.
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