In the years following 9/11, Michael Ratner, who has died of cancer aged 72, emerged as one of America’s foremost human rights lawyers. He galvanised 500 US lawyers of various political persuasions to challenge the legality of holding hundreds of Muslim men, arrested around the world, without charge or trial in Guantánamo Bay. He served as president and later president emeritus of the New York-based Center for Constitutional Rights (CCR), founded in 1966 by the leftwing lawyer William Kunstler and others who represented the civil rights movement in the southern states in its most challenging years. Ratner worked there for 40 years, and his leadership made CCR the focal point for the lawyers who went to Guantánamo to represent unknown prisoners from a dozen countries, and then a leading voice for closing the detention camp.