The norm among many countries that find treasonous citizens in their midst is to punish them - sometimes meting out the greatest punishment there is - but they do not revoke their citizenship.
Philippe Petain and his colleague, politician Pierre Laval, are considered the most abominable traitors in the history of their country, France. They collaborated with the Nazi occupier during World War II and established the Vichy regime, which danced to Hitler's tune. Vidkun Quisling played a similar role in Norway during the same period, and he has been so disgraced that his name has become an international synonym for traitor.
After the Nazis were defeated, the three traitors were sentenced to death (though Petain's sentence was reduced to life in prison). But during their trials, no one demanded that they be shorn of their citizenship. That is also the norm among other countries that find treasonous citizens in their midst: They punish them - sometimes meting out the greatest punishment there is - but do not revoke their citizenship.
In Israel, in contrast, there has been a trend in recent years toward treating citizenship like a conditional right that can be revoked for various reasons. Until recently, Israeli law gave the interior minister the authority to revoke a person's citizenship due to "breach of trust to the state" or "unauthorized travel to an enemy country" (this law was amended in late July to limit this authority and transfer it to the courts, but citizenship can still be revoked). Interior ministers never really used this power until 2002, when Eli Yishai, who was interior minister at the time, applied it to two Israeli Arabs: Keis Obeid, who defected to Lebanon and joined Hezbollah's leadership, and Nihad Abu Kishak, who was suspected of Hamas membership and involvement in terrorism. This sanction was possible not only because of Yishai's temperament and worldview, but also because the public and the Knesset sought to frighten Israeli Arabs.
Indeed, this is the law's major weakness. Although it appears to be objective, it actually targets a specific population: Arab citizens of Israel. There has never been a demand to revoke the citizenship of Jewish spies or traitors (and there have been a few of those), or of Jewish criminals whose acts were considered a blow to the foundations of the state's existence (like Yigal Amir). This demand consistently arises only in connection with treasonous acts or collaboration with the enemy by Arab citizens. The latest of these is Azmi Bishara, though this week the High Court of Justice rejected a petition to revoke his citizenship (and pension benefits).
Bishara's behavior is indeed outrageous, but is it any worse than that of Jewish spies Marcus Klingberg or Israel Beer, who passed highly confidential state secrets to the Soviet Union? And how is Mordechai Vanunu's treason less serious than that of the two Arab terror operatives whose citizenship Yishai revoked? Why is it that when the treasonous act is attributed to Arabs, the state does not suffice with punishing them in accordance with criminal law, but instead indicates willingness to subject them to the additional punishment of revoking their citizenship?
As noted by a recent research paper published by the Israel Democracy Institute ("An Israeli, even though he has sinned, is still an Israeli? Revoking citizenship on grounds of disloyalty," by Efrat Rahaf, supervised by Mordechai Kremnitzer), citizenship is a status that intensifies the rights and obligations of individuals toward their countries. The revocation of citizenship is included in democratic countries' repertoire of permissible punishments, but it is bounded by significant limitations. For instance, it is accepted practice that a country does not revoke someone's citizenship if he lacks any other citizenship. In any case, in democratic countries, revoking citizenship is an option only in cases of treason. In no developed country is "unauthorized travel to an enemy country" a reason for revoking citizenship.
Israel has a wide variety of sanctions with which it can punish citizens involved in terrorism or aiding enemy countries, and there is no need to add the revocation of citizenship to that list. Depriving Israelis of their citizenship is primarily a way of giving vent to vengeful urges, and its significance is more symbolic than practical. (After all, Bishara fled the country and acts like he has turned his back on Israel.)
Under the present circumstances, the damage caused by leaving the legislation as it stands (and proposing other bills in the same spirit) is immeasurably greater than any apparent benefit. It strengthens Israeli Arabs' feelings of discrimination and increases the chances that citizenship will be revoked arbitrarily if the prosecution does not have enough evidence to convict treason suspects in ordinary criminal proceedings.