The other night they returned a bunch of empty tear gas canisters, all marked "made in USA," fired by Israeli soldiers in the West Bank. They're used to break up nonviolent protests against the Israeli-built wall that is tearing Palestinian life apart.

One canister made in the USA killed Jawaher Abu Rahmah, in the village of Bil'in, on the last day of 2010. Another one killed Jawaher's brother, Bassem, in April, 2009.

Apparently the ambassador did not appreciate the courteous gesture. The police quickly arrived, broke up the action, arrested eleven people, and found a way to keep them jailed on trumped up charges.

But these canisters, and the Israeli soldiers who shoot them, don't discriminate against Palestinians. American-made tear gas canisters are used against American citizens too.

Just a few days before Bassem Abu Rahmah was killed by a tear gas canister blow to the chest, an American volunteer with the International Solidarity Movement, Tristan Anderson, was hit in the head by the same kind of canister in the village of Ni'lin. Anderson survived, though surgeons had to remove part of his brain. Another American, Emily Henochowicz, lost her eye in June 2010 when she was hit by a tear gas canister during a protest at a West Bank checkpoint.

The victims of all these tragedies were strictly nonviolent and posed no threat to the Israeli soldiers.

The Israelis used two kinds of tear gas canisters on New Year's Eve when Jawaher Abu Rahmah died. One photographed by Joseph Dana, media spokesman for the Popular Struggle Coordination Committee, had the letters "CTS" stamped on it.

CTS, Combined Tactical Systems, is a brand name used by Combined Systems Inc. based in Jamestown, Pennsylvania (though the American company is owned by an Israeli, according to Dana). There's plenty of evidence that the Israelis get tear gas from CSI. It was a CTS canister that killed Bassem Abu Rahmah.

The Israeli military also used lethal high-velocity projectiles at Bil'in, the kind that struck Bassem Abu Rahmen and Tristan Anderson, although they are supposedly banned by the Israeli Defense Forces. These are also made by CSI. An aluminum canister like the ones made by CTS took out Emily Henochowitz's eye.

The grenade photographed at the New Year's Eve protest appears to be what CTS calls a "Tear-Ball Grenade." Another activist who was there, Jeff Klein, was photographed holding a Tear-Ball Grenade that he says had the letters "CTS" stamped on it. It spins through the air and then bounces along the ground, so no one can predict where the gas will spew out. CSI says that the Tear-Ball can be loaded with either CS (a strong tear gas), OC gas (more commonly known as pepper spray), or CN gas (mace).

Ha'aretz, Israel's most respected newspaper, reported that Jawaher was killed by CS gas. "Protester death shows IDF may be using most dangerous type of tear gas," the headline read. It's the kind of gas the Israelis usually use, the report explains, even though "there have been reports of several deaths caused by the inhalation of CS."

However, after Jawaher died her cousin Hamde Abu Rahmah said, "We deal with tear-gas on a regular basis but the amount that they used and the strength was something we have not yet seen." Others at the New Year's Eve protest agreed. One said that the gas felt "like a million blue shards of glass tearing at your alveoli and shredding your eyes... Every breath tears at your insides; vicious animals live in your lungs. I'd rather not breathe than take one more anguished, searing, charred breath. Then, you don't have a choice; you can't breathe."

Ahmad el-Jobeh believes it was pepper spray that cost him his eyesight when he was accidentally caught up in Israeli repression of a protest in Silwan, an Arab section of Jerusalem where Jews join Palestinians regularly to protest the destruction of Arab homes and construction of Jewish dwellings. There's no doubt that some tear gas canisters used in Silwan, whatever is in them, are marked"Made in U.S.A." and say clearly that aiming them at people can be lethal. What's worse, the gas in some of them, at least, is past its expiration date and thus even more dangerous.

The IDF is trying to deny responsibility for Jawaher Abu Rahmah's death, claiming she was not even at the protest. But there are eyewitnesses who saw her there, saw her taken away in an ambulance, and can disprove virtually every piece of the IDF's concocted story. With so many past instances of IDF cover-ups proven false, it's hard to take this self-serving story seriously. The editors of Ha'aretz assume it's not true. And some Israeli military officers dismiss it as "mere thoughts."

But the most telling fact is that the debate about the IDF story has provoked more interest in Israel than Jawaher's death itself. The dominant concern in Israel is not for the obvious evils of the occupation but for Israel's public image.

The IDF is in a bizarre position -- telling the world to ignore the unprovoked tear gas attack, ignore the wall that Israel's Supreme Court has ruled illegal in Bil'in, ignore the confiscation of Palestinian land to enlarge settlements that the whole world says as illegal, and see Israel as totally innocent simply because Jawaher was at home when the Made-in-USA gas killed her.

Suppose she was in her home in the small village, a few hundred yards from the front of the protest. Tear gas does float through the air. Even if the Israelis could prove their claim true, the IDF's PR barrage and the focus on that one detail of the story shows a depressing moral bankruptcy.

So what's a U.S. citizen to do? There is a growing boycott/divestment/sanctions (BDS) movement aimed at Israel. But can we boycott the tear gas makers? Though they make an amazing variety of other products too, all are used by military forces, or by police departments. Nothing you'd be likely to buy.

However, you might check whether your local police department is patronizing Combined Systems, Inc. with your tax dollars. CSI says that it markets "its innovative line of less-lethal munitions" -- less lethal than what? -- "and crowd control products to domestic law enforcement agencies under its law enforcement brand name, CTS." Even the moderate Jewish peace group J Street, which has serious reservations about BDS, says it takes a positive view of targeted boycotts aimed only at the occupation.

J Street itself is more interested in putting pressure on the Obama administration to take "a bolder, more assertive approach" to the peace process. It wants the U.S. to lean on the Israelis and Palestinians to quickly negotiate the borders of the new Palestinian state. If the parties can't do it themselves (which seems likely) the U.S. should present its own proposal, J Street says -- an idea that's rapidly gaining a lot of support.

There's no need for peace activists to decide between supporting a targeted boycott and a U.S. peace plan, nor to squabble over which approach is better. The two paths can, and should, be taken simultaneously. They reinforce each other. Israeli and American BDS supporters will keep calling attention to U.S. complicity in the repression and killing of Palestinians. The embarrassments to the U.S. -- like the protest at the American ambassador's home in Israel -- will keep on mounting. Eventually, the Obama administration will find it impossible to let the conflict go on.

The U.S. government has played a central role in perpetuating this injustice. The U.S. government must take responsibility for righting the wrong and ending the killing. It's one of those happy occasions were morality and self-interest both dictate the same policy.

The U.S. government can guide (to put it politely) the Israelis to make fundamental changes because ultimately Israel must bend to U.S. wishes, if the Obama administration asserts itself strongly enough. Whether that happens depends strictly on the administration's political cost-benefit calculus.

Boycotts may or may not ever make the Israelis change their policies. But they might make U.S. companies stop dealing lethal material to Israel. And political pressure -- if it's strong and smart enough -- can make the administration change its ways.

Ira Chernus is Professor of Religious Studies at the University of Colorado at Boulder. Read more of his writing on Israel, Palestine, and the U.S. on his blog.