That's Huwaida Arraf, a co-founder and central figure in the International Solidarity Movement and, recently, the Free Gaza Movement (the folks organizing the boat trips from Cyprus to Gaza). Here's her Wikipedia bio:
Huwaida Arraf (born 1976 in Detroit, Michigan) is a co-founder of the International Solidarity Movement (ISM), a pro-Palestinian organization. The stated mission of the ISM is to resist the Israeli occupation using nonviolent tactics. Arraf is married to Adam Shapiro, another ISM co-founder, whom she met while both were working at the Jerusalem center of "Seeds of Peace", an organization that seeks to foster dialogue between Jewish and Palestinian youth.
Arraf, who is Christian, is the daughter of a Israeli Arab father and a Palestinian mother. Arraf majored in Arabic and Judaic studies and political science at the University of Michigan, Ann Arbor. She also spent a year at the Hebrew University in Jerusalem and studied Hebrew on a kibbutz.[1].
Huwaida later earned a JD at American University's Washington College of Law. Her focus was on International Human Rights and Humanitarian Law, with a particular interest in war crimes prosecution.
>WOW!!!
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>What appears to be an American young woman stands in front of Israeli soldiers blocking them from shooting Palestinian protesters in Gaza.
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>This is taken by Korean camera people.
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>This is what courage looks like!
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>http://www.youtube.com/watch?v=SQyIKyd2gqA
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>THANK YOU!
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>Mitchel Cohen
>Brooklyn Greens/Green Party