The political left in Israel has lauded Thursday's ruling, describing it as a "blow to the Jewish settlers' messianic aspirations".
"This ruling ends any question or doubt as to the legitimacy and legality of the disengagement from Gaza. The High Court is the highest judicial body in Israel, and the settlers and their supporters must respect its rulings," said Zahava Galon, Knesset member and spokeswoman for the centre-left Yahad party.
"They should stop claiming that the planned pullout violates their human rights and constitutes a form of ethnic cleansing."
In ruling the withdrawal legal, the court said the West Bank and Gaza Strip, which Israeli occupied from Jordan and Egypt respectively 38 years ago, were not parts of Israel.
Palestinians were lukewarm about the ruling.
"They [settlers] should stop claiming that the planned pullout violates their human rights and constitutes a form of ethnic cleansing"
The Palestinian Authority reacted cautiously, saying there was "brazen duplicity between what the High Court says and what the Israeli government is doing on the ground".
"We all know that the West Bank and Gaza and East Jerusalem are not parts of Israel. The question which should be addressed is why the occupation of these territories continues," said a Palestinian Foreign Ministry spokesman Majdi al Khalidi.
He stressed that "our reference is not Israel and its courts, but the International Court of Justice and international law".
Other Palestinian leaders saw nothing new in the ruling.
"There is nothing new in this ruling. Israel has not officially and formally annexed the West Bank, but at the same time it built hundreds of Jewish colonies in this occupied territory," said Mustafa al-Barghuthi, head of the Palestinian Democratic Initiative and former presidential candidate.
"If the court is really true to its ruling, then why doesn't it rule that this apartheid wall and these settlements are also illegal and ought to be dismantled as the International Court of Justice ruled," said al-Barghuthi.
Israeli settlers have vowed to
oppose the pullout plan
The international court in June 2004 ruled that the "separation wall" was illegal and ought to be dismantled and that all of the West Bank, East Jerusalem and Gaza Strip were occupied territories pursuant to international law.
However, Arab Knesset member Talab al-Sanei', himself a lawyer, viewed the court decision as "an significant precedent" and "a step in the right direction".
"We consider this ruling a vindication of our constant stand that occupation is illegal, illegitimate and must end sooner than later."
But the Arab Knesset member added that "we shouldn't give this ruling more attention than it deserves".
"It doesn't mean that Israel will wake up tomorrow and decide to end the occupation. The judicial apparatus in Israel is ... used to give the occupation and the administration of oppression a legal facade."
The settlers and their supporters have dismissed the ruling as irrelevant and unacceptable.
The separation wall was ruled
illegal by the ICJ in 2004
"We didn't expect anything from this court since the petitioners are Jews and patriots," said Yoram Sheftel, an attorney for the Gaza settlers. "This was fully expected, there is no surprise, and I am not disappointed because we didn't have any expectations."
Other settler leaders in Gaza vowed to resist the expected evacuation, arguing that their right to the land overrides any ruling by the High Court.
"We have a ruling from God to possess this land," said a settler named Yoram in a telephone interview from Gaza.
Since 1967, Israel has refused to apply Israeli law to the occupied Palestinian territories, except East Jerusalem, which was annexed shortly after the war.
The Jewish state has been applying Israeli law to hundreds of thousands of settlers living in 280 colonies and colonial outposts in the West Bank and Gaza, while imposing stringent laws, some of which date to the Ottoman and British mandate era, on the estimated 3.7 million Palestinians.
Israel fears the application of Israeli law to these Palestinians would confront the Jewish state with two stark choices: to grant Palestinians Israeli citizenship, which would end Israel's Jewish majority, or risk becoming an apartheid state.
Israeli leaders, including Prime Minister Ariel Sharon, have sought to justify the planned withdrawal from the Gaza Strip by arguing that this measure would prevent Israel from becoming a bi-national state as well as help consolidate the occupation of the West Bank.