Like a modern-day Cain, Mordechai Vanunu walks the streets of East Jerusalem in search of a place to spend the night. He has no permanent address, and because of a cash shortage he moves from one cheap hostel to the next. He is forbidden to talk with foreigners. With Israelis he does not wish to speak. The Arabs in East Jerusalem do not try to befriend him, fearing trouble. He is a difficult and complicated man. His belief in his principles is stern and dogmatic, but is also cause for bewilderment. Even his family and most of his few supporters abroad have cut off contact.

His financial situation as well as his physical and mental health is deteriorating. But Israel, to paraphrase Gene Pitney, is "a state without mercy." The security authorities and the courts, which back them almost automatically, are time and again after him. This is a vindictive, closed system that intends to apply the law as severely as possible. This week Home Front Command, one of the authorities dealing with Vanunu's case, called in his attorneys Avigdor Feldman and Michael Sfard to tell them that the warrants restricting Vanunu's freedom of movement and speech will remain unchanged. A similar announcement will be made by the Interior Ministry. Moreover, Vanunu still faces a four-month prison term for violating the restrictions - because he tried to enter Bethlehem on Christmas and spoke with foreign reporters. He has appealed to the Supreme Court.

Thus Vanunu, who was released from prison in 2004, entered his sixth year as a "Prisoner of Zion." During that time we have had three prime ministers, four justice ministers and three defense ministers; Israel exchanged prisoners with Hezbollah; spies were released from prison and murderers' sentences were shortened. But the state is adamant that Vanunu be punished repeatedly for his original sin.

The authorities consider him a traitor, even though he did not betray secrets to enemy countries, a terrorist organization or foreign security organizations. He exposed Israel's nuclear secrets to the British Sunday Times. Even if we accept the state's stance that this makes him a spy and a traitor, he was neither the worst nor the most dangerous. There have been and there are worse traitors than Vanunu.

Indeed, he violated the law and he deserved his punishment. But he already served his 18 years in jail, partially under cruel solitary confinement. Nonetheless, the state refuses to allow him to leave the country and start life anew. He may still have time to start a family. After all, it is an accepted legal norm that a person not be punished twice for the same crime.

It used to be that the state's vengeful treatment of Vanunu was attributed to the chief of state security, Yehiel Horev. I thought so, too. I admit I was wrong. Horev has been gone for nearly two years. And still, his replacement Amir Kain holds the same view: None of the restrictions imposed on Vanunu should be lifted, and he must not be allowed to leave Israel.

The justifications are weak and exaggerated. The claim is that Vanunu holds more secret information about Israel's nuclear program. The entire world assumes Israel has nuclear weapons, so what further damage can he cause to the security of the state? Based on this logic, he may never leave Israel.

Every person, regardless of his views, with a conscience, ethics and a sense of justice must tell the state, enough. No more. After 23 years of suffering, let Mordechai Vanunu become a free man.