In a continuing legal saga, a Jerusalem court on Tuesday heard an appeal by Mordechai Vanunu against a six-month jail sentence for violating the conditions of his release from prison by maintaining unauthorized contact with foreigners. The latest legal battle comes more than four years after Vanunu was released from prison after serving a 18-year prison sentence, including more than 11 years in solitary confinement, for revealing Israel's secret nuclear program. According to the terms of his release, Vanunu, 53, is barred from leaving Israel by order of defense officials who argue that he has more state secrets to spill, and is also required to seek official permission for all contacts with foreigners. Last year, the Jerusalem Magistrate's Court sentenced Vanunu to half a year in jail after he repeatedly and openly violated the ban on speaking to foreigners without authorization. The ban, which is in effect through October but has been repeatedly renewed over the last four years, had been approved by the Israeli Supreme Court. "This is an unprecedented ban in the State of Israel which in essence isolates the appellant from human society and cuts off his oxygen," Vanunu's attorney, Avigdor Feldman, argued in the Jerusalem District Court. The high-profile Israeli defense attorney told the appeals court that his client had violated the ban "tens of thousands" of times by speaking to foreigners, including the owner of his flat, and even for exchanging pleasantries with the small group of international supporters who converged on the Jerusalem courtroom on Tuesday. "Vanunu has become a symbol for persecution, and this court cannot lend its hands to such a grotesque [ban]," Feldman told the three-judge panel hearing the appeal. In contrast, state prosecutor Dan Eldad told the court that the ban on contact with foreigners was issued as a result of security concerns, and that the punishment fit the crime. "The ban [on contact with foreigners] was issued on the basis of a security necessity, and the sentence handed down is meant to prevent the appellant from continuing to repeat these crimes," Eldad said. He noted that a police officer had been allocated to deal with any and all requests by Vanunu to contact foreigners, and that all the requests he had filed with his police liaison - save one - were approved. Accusing Vanunu and his attorneys of making wisecracks, Eldad said that the ban was not intended to bar Vanunu from day-to-day conversation with foreigners, but to prevent him from discussing his work as a former nuclear technician or other security-related issues. Vanunu's revelation of Israel's nuclear secrets in in a 1986 interview with The Sunday Times and his subsequent imprisonment made him a hero to international anti-nuclear and far-left activists alike. Over the last four years, Vanunu, a Jewish convert to Christianity who is widely reviled by Israelis, has repeatedly expressed his desire to leave Israel, asserting that he has no more secrets to reveal. But Israel's Supreme Court has repeatedly extended restrictions preventing Vanunu from traveling abroad, or maintaining contacts with foreigners, on the grounds that he still represents a threat to state security. Several unauthorized interviews he had given to the international media about Israel's nuclear program quickly landed him back in court. Israel maintains a policy of nuclear ambiguity - it refuses to confirm or deny whether it has nuclear weapons. The court, which repeatedly peppered the attorneys for both sides with questions during the nearly two-hour afternoon hearing, will hand down its ruling on the appeal at an unspecified date. If the court turns down the appeal, Vanunu could still turn to the Supreme Court in a last-ditch effort to stay out of jail.