Notwithstanding the UN Secretary General’s statement, Israel claimed self-defense, as the air strikes followed a rocket attack from Gaza that killed an Israeli civilian in the border town of Sderot. However, in his book Crimes of War , Michael Byers, a Duke University law professor, argues that the use of force in self-defense “must not be unreasonable or excessive,” and with regard to anticipatory action, the necessity must be “instant, overwhelming, leaving no choice of means, and no moment of deliberation.”