Whilst at university he became involved in the non-violent protests organised by the Northern Ireland Civil Rights Association.[3] Maginness participated in the famous civil rights march in Derry in 1972 at which British troops killed 14 unarmed civilians.[citation needed] This event, now termed Bloody Sunday, has gone down in Northern Ireland politics as one of the turning points in The Troubles that contributed to the development of the Provisional IRA.
In November 2008 Maginness had his trademark moustache shaved off for the BBC's Children in Need.[6]
Maginness was the SDLP candidate for the 2009 European Election.
Maginness accused the Secretary of State of interning dissident republican Marian Price without trial, saying "We do not support putting people away in prison because of intelligence or because of some political point of view and we are convinced that she has been detained without trial because of that by the secretary of state."[7]
Having served as an MLA for North Belfast from 1998, Maginness decided not to stand for election in 2016.[8] He was replaced by Nichola Mallon.