About four years ago now, a group of people dressed up as zombies to protest mindless consumerism at a mall. They were arrested and jailed on the grounds that they possessed items resembling weapons of mass destruction (an iPod with speakers). Anyway, they've won their court battle against the city of Minneapolis.
Mokalus of Borg
PS - There were only seven people in the group.
PPS - So I guess their protest didn't look very much like one.