The brief that persuaded the Supreme Court to strike down America's last laws against interracial marriage was written not by a seasoned civil rights litigator but by a lawyer only a few years out of law school. William D. Zabel, who spent the next six decades building both an elite Manhattan law practice and one of the nation's most durable human rights institutions, died in July 2026, Human Rights First announced. He was in his late eighties.

Zabel's path to that brief began in 1955, when the murder of Emmett Till and the acquittal of his killers by an all-white jury reached him as a Princeton University sophomore. He and his roommate circulated a petition urging the Justice Department to prosecute the men responsible. Among those who signed was Albert Einstein, then a professor at Princeton's Institute for Advanced Study, whose name helped draw attention to the effort. Nine years later, in the summer of 1964, the young lawyer traveled to Mississippi to help secure the release of Black citizens who had been jailed for registering to vote. He was harassed, threatened, and shot at by members of the Ku Klux Klan while there.

By 1965 he had turned that experience into an argument, publishing an article in The Atlantic titled "Interracial Marriage and the Law" that challenged the constitutionality of laws banning such unions. He went on to write the lead brief on behalf of the ACLU in Loving v. Virginia, and in 1967 the Supreme Court ruled unanimously that marriage bans still on the books in sixteen states were unconstitutional.

Two years later, in 1969, Zabel co-founded the New York firm Schulte Roth & Zabel, where he headed the Individual Client Services Group and spent the rest of his career advising clients on trusts, estates, and family law. He was a life member of the American Law Institute.

Alongside that practice, Zabel gave more than twenty years to chairing the board of Human Rights First, which he had helped guide since its earliest years. He traveled on the organization's behalf to investigate abuses in the Soviet Union, the Philippines, and China, and in 1989, as the Iron Curtain came down, he and Human Rights First co-founder Tom Bernstein went to Moscow to examine the rights situation there. In Pinochet's Chile, he investigated the disappearance of lawyers and judges and helped secure safe haven in the United States for Judge Carlos Cerda, who had been targeted by the regime.

Zabel built Human Rights First's pro bono legal network into one that, by 2024, connected thousands of volunteer lawyers to clients from 83 countries and delivered 85 million dollars in free legal services in a single year, according to the organization. In January 2014 he helped launch the Immigrant Justice Corps as its founding board chair, alongside federal appeals judge Robert Katzmann and former Manhattan district attorney Robert Morgenthau. The organization trains and places lawyers to represent immigrants facing deportation, and it has reported a 93 percent success rate in completed cases with representation, compared with 15 percent for those without a lawyer. Zabel remained involved as board chair emeritus. In September 2018, Human Rights First renamed its annual honor the William D. Zabel Human Rights Award in recognition of his decades of leadership. He also endowed a human rights professorship at Harvard Law School, later held by former U.S. Ambassador to the United Nations Samantha Power, according to Harvard Law School. In December 2023, Princeton University announced a gift from the JPB Foundation establishing the William D. Zabel '58 Professorship of Human Rights, named for the Princeton class he had entered nearly seven decades earlier.

Zabel kept practicing law into his late eighties. "I'm never going to retire. I'm addicted to the law," he said in a 2023 Princeton University profile. Asked what he was proudest of, he pointed back to the case that had started it all: "I'm most proud of Loving v. Virginia because that goes in the history books."

News of his death drew tributes from colleagues who had worked beside him for decades. "Bill was one of a kind. He was a lion who put his heart and soul into Human Rights First from day one," said Tom Bernstein, the organization's chair emeritus. Michael Posner, its founding executive director, said: "Bill's passion for justice took him from Mississippi to Moscow, with many stops along the way. He was a kind and decent man who was an extraordinary champion for human rights."

What Zabel built endures in concrete form: the firm that carries his name, a Supreme Court brief still cited wherever marriage rights are argued, a professorship at Harvard and another taking shape at Princeton, and a pro bono legal network still connecting volunteer lawyers to human rights clients in dozens of countries.