Kids In Need of Defense, an immigration advocacy group where Osuna's widow, Wendy Young, serves as president, confirmed the death to Law360 on Friday. Osuna's age and official cause of death were not immediately available.

Osuna, who left the EOIR in May, had an "unparalleled" concept of the nation's immigration court system, said Mariaelena Hincapie, executive director of the National Immigration Law Center.

"Juan Osuna will be remembered as a tireless and dedicated advocate for justice for immigrants," Hincapie said. "He was thoughtful, scholarly and kind in his pursuit of a just and fair court system."

Osuna was appointed a member of the Board of Immigration Appeals in 2000 and went on to serve as its chair before shifting in 2009 to the DOJ's Civil Division. There, he was responsible for the Office of Immigration Litigation and for overseeing immigration policy and other matters, according to Georgetown University Law Center, where Osuna served as an adjunct professor.

While EOIR director, Osuna told lawmakers in December 2015 that a massive immigration court backlog was largely due to a shortage of judges, particularly after many left between 2011 and 2014 and the agency was stymied in replacing them by budget cuts.

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