Bombshell actress and Obama campaigner Scarlett Johansson surprised plenty of people today by parting with the social justice charity Oxfam over her decision to star in a series of ads promoting Sodastream, an Israel-based company. What the hell happened? Here's everything you need to know.

Okay, what's Oxfam, and how was ScarJo involved with it?

Oxfam is a collection of anti-poverty, pro-human rights charities that (among other things) pushes fair trade and watchdogs major corporations. It was originally formed in England during World War II by Quakers and their friends as the Oxford Committee for Famine Relief, to make sure civilians in the Axis countries were getting enough to eat as the Allies bombed them.

Oxfam gets a lot of help from celebrities to raise cash and awareness. The top tier of celeb supporters gets anointed Oxfam Ambassadors; that circle has included Annie Lennox, Bill Nighy, Coldplay, Minnie Driver, and—from 2007 until today—Johansson. In eight years, she's worked on a host of issues for the group, from disaster relief to education for women to food justice and donation campaigns. She's even auctioned herself off—well, a date with her, anyway—for the group.

Sounds like a cool gig. Why'd Johansson kick it?

ScarJo recently signed on to be a spokeswoman for SodaStream, the makers of that in-home DIY soda kit. (The faux-racy ad above, from that campaign, is billed by the company as a "Super Bowl commercial" that was rejected by Fox because it trashes Coke and Pepsi, major sports sponsors.)

Yeah, so a star's gotta get paid. What's wrong with that?

Ever since a 1991 merger, SodaStream has been headquartered outside the Tel Aviv Airport in Israel, but its main production plant is across the Green Line in an industrial section of a West Bank settlement, which is seen as illegal by international law and a big sticking point in Israeli/Palestinian relations.

Oxfam is not too keen on that situation, as it made clear in its statement announcing Johansson's resignation from the group:

While Oxfam respects the independence of our ambassadors, Ms. Johansson's role promoting the company SodaStream is incompatible with her role as an Oxfam Global Ambassador.

Oxfam believes that businesses, such as SodaStream, that operate in settlements further the ongoing poverty and denial of rights of the Palestinian communities that we work to support.

Oxfam is opposed to all trade from Israeli settlements, which are illegal under international law.

So rather than quit the ad campaign, Johansson quit the charity? Is she for real?

No one can be sure of Johansson's deepest intentions, but the split has been amicable, at least in public. And it was probably an untenable situation: Even if Johansson had spurned SodaStream overnight, her work with the company would probably have stuck in the craws of many groups and individuals upon whom Oxfam depends. The breakup maximizes Oxfam's credibility with those groups, and ends the controversy fairly quickly.

Okay, but who's in the right here?

Depends on where you stand. Johansson argues that the SodaStream plant is exactly what the sides need in Israel and Palestine. "I remain a supporter of economic cooperation and social interaction between a democratic Israel and Palestine," she said in a statement announcing her split with Oxfam:

SodaStream is a company that is not only committed to the environment but to building a bridge to peace between Israel and Palestine, supporting neighbors working alongside each other, receiving equal pay, equal benefits and equal rights. That is what is happening in their Ma'aleh Adumim factory every working day.

For his part, SodaStream CEO Daniel Birnbaum calls the company's West Bank factory "a pain"—it was built there more than 20 years ago, before his time, and he says that, had he been given the choice, he wouldn't have set up shop there. But, he argues, it's employed 500 Palestinians for years, and they'd be screwed now if the company picked up and left to satisfy political activists.

"We will not throw our employees under the bus to promote anyone's political agenda," he told the Forward recently. "[I] just can't see how it would help the cause of the Palestinians if we fired them." An advisor for Birnbaum added that inside the company, "everybody is against the occupation."

So the plant and the company are good for Palestinians?

Maybe. (shrugs) Keep in mind that Johansson and Birnbaum have financial incentives to boost SodaStream's efforts. And activists counter that the benefits to Palestinians are overblown. "All of the work in this factory is actually benefiting from exploiting Palestinian workers as cheap labor and Palestinian land for the establishment of the factory, and enjoys benefits and funding from the Israeli government," Rona Martin of the Coalition of Women for Peace told NPR last year. CWP has also worked with Oxfam.

Is there any precedent for all this?

With Oxfam, yeah, totally. Sex and the City's Kristin Davis had been an Oxfam Ambassador, doing AIDS awareness trips to South Africa for the group, but they distanced themselves from her in 2009 after she took a (short lived) job as a spokeswoman for Ahava Dead Sea Laboratories. Her contract with Ahava has run out, and she's since returned to Oxfam's good graces.

So who knows? Maybe all will be forgiven with ScarJo... once the fuss subsides, and the settlements questions are answered for good. On second thought, don't hold your breath. Just kick back with a drink. Only don't make it a soda, because it sucks for your gut, and frankly, all those companies are terrible.

In the meantime, she'll probably have to contend with more memes like this:

This post has been updated to clarify that while SodaStream is headquartered in Israel, the settlement containing the production plant in question is outside Israel and in the occupied West Bank.