Michael Ratner, the civil and human rights attorney who represented Julian Assange and WikiLeaks in the US, died Wednesday at age 72, leaving behind an outsized legacy of advocacy for whistleblowers and US government detainees.

“As an attorney, writer, speaker, educator, activist ... Michael Ratner’s passion was not just for the law but for the struggle for justice and peace,” said the Center for Constitutional Rights, a not-for-profit legal advocacy organization where Ratner worked to bring cases for 45 years. “Michael dedicated his life to the most important fights for justice of the last half century.”

Ratner joined CCR in 1971 after graduating from Columbia law school, just a week before the famous prisoner revolt at the Attica correctional facility in upstate New York. The case of the Attica brothers versus then governor Nelson Rockefeller would be Ratner’s first for the organization.

A tireless critic of extraordinary rendition and indefinite detention throughout the post-9/11 war on terror, Ratner was co-counsel in a 2004 suit filed on behalf of captives at Guantánamo Bay that reached the supreme court. In a landmark decision, the justices decided in Rasul v Bush that detainees did have the right to challenge their detention and that US courts have the jurisdiction to hear those complaints in the case of foreign nationals.

Michael Ratner. Photograph: The Guardian

Ratner was also a founding member of the Guantánamo Bay Bar Association, a group of more than 500 attorneys who provided pro-bono representation to detainees, an effort CCR calls “the largest mass defense effort in US history”. Long before the war on terror, Ratner took up the cause of Guantánamo detainees in the 1990s, winning the closure of a detention camp set up exclusively for holding HIV-positive Haitian refugees.

During his career, Ratner sued three US presidents: Ronald Reagan, Bill Clinton and George W Bush, and passionately argued for the impeachment of the latter for warrantless surveillance, torture, misleading Congress about the Iraq war, and violating the constitution’s separation of powers.

Ratner returned to Columbia as an adjunct professor, also teaching at Yale during his career and serving as president of the National Lawyers Guild from 1982 to 1983. Ratner published several legal books and received awards for excellence from Trial Lawyers for Public Justice and the Columbia Law School Public Interest Law Foundation.

A sometimes contributor to the Guardian, which first reported the NSA surveillance revelations made by Edward Snowden, Ratner was a frequent defender of whistleblowers against US national security secrecy. Opining on the legal status of Snowden, Chelsea Manning, and his client, WikiLeaks founder Assange, Ratner said all of them “did their civic duty by disclosing information on government overreaching. They all exhibited great moral courage in doing so. And they all deserve far more than unfair imprisonment and exile for the service they have done for the American people and for people all around the world.”

In its statement, CCR said: “Michael’s leadership and generous spirit have shown the way for new generations of social justice lawyers,” adding “[t]oday we mourn. Tomorrow we carry on his work.”