Youssef Magied al-Molqui was released from a Palermo prison and a judge had ordered him expelled from Italy.
Al-Molqui, who is married to an Italian woman, served nearly 24 years of a 30-year sentence handed down by an Italian court after the hijacking. He was released early for good behavior.
During the action, four Palestinians shot dead an American Jew, Leon Klinghoffer, who was in a wheelchair, and threw his body overboard. His corpse washed ashore several weeks later.
Al-Molqui was held principally responsible for the murder and is believed to be the last of the four hijackers who was in prison.
Klinghoffer’s killing was discovered after the hijackers allowed the ship to dock in Egypt and they initially managed to escape.
Later, U.S. fighter jets intercepted an Egyptian plane on which the hijackers were trying to flee and forced it to land in Sicily, where the four hijackers were arrested.
Relations between Italy and the United States nosedived at the time because Italy allowed Palestinian guerrilla leader Abu Abbas, who had masterminded the hijacking and who was aboard the Egyptian plane, to escape to then-Yugoslavia.
In 1996, al-Molqui failed to return to prison after a 12-day leave. He was later arrested in Spain. At the time, the United States put a $2 million bounty on his head.