A U.S. federal high court rejected an appeal Thursday against the extradition of two men to Japan to face charges over allegedly helping former Nissan Motor Chairman Carlos Ghosn flee the country in December 2019.

The federal high court in Boston upheld a district court ruling in late January that Michael Taylor, a 60-year-old former Green Beret, and his 27-year-old son Peter Taylor should be handed over to Japanese authorities.

Carlos Ghosn speaks during a press conference in Beirut in January 2020. (Anadolu Agency/Getty/Kyodo)

The district court ruling came after the State Department approved the extradition of the two men last October at the request of Japanese law enforcement authorities.

It remains unclear whether the U.S. government will extradite them soon.

The defense team for the two men has argued that they could receive inappropriate treatment amounting to torture if they are sent to Japanese authorities.

Since Ghosn's departure occurred at a time when he was lawfully freed on bail, the act itself does not constitute a crime in Japan, and therefore it is not appropriate to charge the two men for their roles in assisting the former auto tycoon's escape, the team has maintained.

Ghosn has claimed that he was detained for an extended period of time under severe conditions in Japan and fled the country to escape what he called a "rigged" justice system.

According to district court documents, the Taylors allegedly helped Ghosn, arrested by Tokyo prosecutors in 2018 and later released on bail, to sneak out of Japan in December 2019 by hiding inside a large box.

Ghosn has remained in Lebanon, where he spent his childhood, after fleeing there via Turkey. Japan does not have an extradition treaty with Lebanon.

Ghosn, who headed Nissan for nearly two decades, was supposed to face trial in Japan on allegations that he misused company funds and understated his remuneration by billions of yen over multiple years.