This article was originally published by the San Francisco Chronicle and is republished with the author's permission.

A Palestinian boy watches the funeral of a man killed in an Israeli military incursion in the southern Gaza Strip. (Hatem Omar, Maan Images)

When does a citizen-led boycott of a state become morally justified?

That question is raised by an expanding academic, cultural and economic boycott of Israel. The movement joins churches, unions, professional societies and other groups based in the United States, Canada, Europe and South Africa.

It has elicited dramatic reactions from Israel's supporters. U.S. labor leaders have condemned British unions, representing millions of workers, for supporting the Israel boycott. American academics have been frantically gathering signatures against the boycott, and have mounted a prominent advertising campaign in American newspapers - unwittingly elevating the controversy further in the public eye.

Israel's defenders have protested that Israel is not the worst human-rights offender in the world, and singling it out is hypocrisy, or even anti-Semitism. Rhetorically, this shifts focus from Israel's human rights record to the imagined motives of its critics.

But "the worst first" has never been the rule for whom to boycott. Had it been, the Pol Pot regime, not apartheid South Africa, would have been targeted in the past. It was not - Cambodia's ties to the West were insufficient to make any embargo effective. Boycotting North Korea today would be similarly futile. Should every other quest for justice be put on hold as a result?

In contrast, the boycott of South Africa had grip. The opprobrium suffered by white South Africans unquestionably helped persuade them to yield to the just demands of the black majority. Israel, too, assiduously guards its public image. A dense web of economic and cultural relations also ties it to the West. That - and its irrefutably documented human-rights violations - render it ripe for boycott.

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What state actions should trigger a boycott? Expelling or intimidating into flight a country's majority population, then denying them internationally recognized rights to return to their homes? Israel has done that.

Seizing, without compensation, the properties of hundreds of thousands of refugees? Israel has done that.

Systematically torturing detainees, many held without trial? Israel has done that.

Assassinating its opponents, including those living in territories it occupies? Israel has done that.

Demolishing thousands of homes belonging to one national group, and settling its own people in another nation's land? Israel has done that. No country with such a record, whether first or 50th worst in the world, can credibly protest a boycott.

Apartheid South Africa provides another useful standard. How does Israel's behavior toward Palestinians compare to former South Africa's treatment of blacks? It is similar or worse, say a number of South Africans, including Archbishop Desmond Tutu, U.N. special rapporteur in the occupied territories John Dugard, and African National Congress member and government minister Ronnie Kasrils. The latter observed recently that apartheid South Africa never used fighter jets to attack ANC activists, and judged Israel's violent control of Palestinians as "10 times worse." Dual laws for Jewish settlers and Palestinians, segregated roads and housing, and restrictions on Palestinians' freedom of movement strongly recall apartheid South Africa. If boycotting apartheid South Africa was appropriate, it is equally fair to boycott Israel on a similar record.

Israel has been singled out, but not as its defenders complain. Instead, Israel has been enveloped in a cocoon of impunity. Our government has vetoed 41 U.N. Security Council resolutions condemning Israeli actions - half of the total U.S. vetoes since the birth of the United Nations - thus enabling Israel's continuing abuses. The Bush administration has announced an increase in military aid to Israel to $30 billion for the coming decade.

Other military occupations and human-rights abusers have faced considerably rougher treatment. Just recall Iraq's 1990 takeover of Kuwait. Perhaps the United Nations should have long ago issued Israel the ultimatum it gave Iraq - and enforced it. Israel's occupation of Arab lands has now exceeded 40 years.

Iran, Sudan and Syria have all been targeted for federal and state-level sanctions. Even the City of Beverly Hills is contemplating Iran divestment actions, following the lead of Los Angeles, which approved Iran divestment legislation in June. Yet the Islamic Republic of Iran has never attacked its neighbors nor occupied their territories. It is merely suspected of aspiring to the same nuclear weapons Israel already possesses.

Politicians worldwide, and American ones especially, have failed us. Our leaders, from the executive branch to Congress, have dithered, or cheered Israel on, as it devoured the land base for a Palestinian state. Their collective irresponsibility dooms both Palestinians and Israelis to a future of strife and insecurity, and undermines our global stature. If politicians cannot lead the way, then citizens must. That is why boycotting Israel has become both necessary and justified.

George Bisharat is a professor of law at Hastings College of the Law in San Francisco, and writes frequently on law and politics in the Middle East.