Tribals gathered in the national capital from across the country with one message -- to free Dr Binayak Sen who has been working for them in Chhattisgarh for 30 years. Sen was arrested in May 2007 under the Chhattisgarh Special Public Security Act for alleged links with Naxals. Under this law, the police can arrest anyone it suspects of planning a crime and keep them in jail for upto seven years with no bail.