When the Italian prosecutor Paolo Giorgio Ferri visited the Metropolitan Museum of Art in 2004, he posed for a picture beside an ancient terra cotta mixing bowl so rare and celebrated that it had held pride of place in the Met’s Greek and Roman galleries for 32 years. Four years later, as a result of Mr. Ferri’s dogged work as an investigator and antiquities hunter with Rome’s Ministry of Cultural Heritage, that object, known as the Euphronios krater, was back on Italian soil, as were scores of other looted treasures that had been acquired by American museums and collectors since the 1960s.

Mr. Ferri, who had recently retired after 45 years as a judicial magistrate, public prosecutor and legal consultant, died on June 14 at a hospital in Rome. He was 72. His family said the cause was a heart attack.

Colleagues say his legacy includes dismantling multinational looting and trafficking rings; recovering tens of thousands of Greco-Roman artifacts from secret storehouses; and compelling what is sometimes called “the great giveback,” a period that began in 2006 and continues to this day, during which American museums have returned at least 120 ill-gotten antiquities valued at more than $1 billion to the Greek and Italian authorities. Fabio Isman, his friend and biographer, stated:

“No one before him had used the courts to attack the art predators and big museums and corrupt dealers. He was very stubborn, and what he did was very daring.”

In an email interview with The New York Times last year, Mr. Ferri said he did not know what to expect in 1994 when he began investigating the theft of a statue from a villa in Rome and its sudden appearance at a Sotheby’s auction in London. After much digging, he said, he discovered that a dozen prominent American museums housed Roman and Etruscan items that Italian officials never knew existed. His list eventually grew to 47 museums worldwide.