Riot police walk in the street as a couple kiss on June 15, 2011 in Vancouver, Canada. Vancouver broke out in riots after their hockey team the Vancouver Canucks lost in Game Seven of the Stanley Cup Finals. (Photo by Rich Lam/Getty Images)

Former conservative minister Kostis Hatzidakis is covered with blood after about 200 leftists attacked him with stones and sticks, shouting: “Thieves! Shame on you!” in central Athens December 15, 2010. (Photo by Yannis Behrakis/Reuters)

A protester wearing a gas mask walks beside a burning van during violent protests against austerity measures in Athens, June 28, 2011. (Photo by Yannis Behrakis/Reuters)

An injured protestor is led away during clashes with police near Tahrir Square on November 23, 2011 in Cairo, Egypt. (Photo by Peter Macdiarmid/Getty Images)

A riot policeman faces off with a protester during a demonstration in downtown Tunis January 18, 2011. (Photo by Zoubeir Souissi/Reuters)

A protester pleads with police during a demonstration near the Occupy Portland encampment November 13, 2011 in Portland, Oregon. (Photo by Natalie Behring/Getty Images)

A Carabinieri (Italian paramilitary police), his face covered with blood, adjusts his helmet during clashes in Rome, Saturday, Oct. 15, 2011. (Photo by Angelo Carconi/AP Photo)

A riot policeman kicks an anti-austerity protester who fell during clashes in Athens' Syntagma (Constitution) square February 10, 2012. (Photo by Michalis Karagiannis/Reuters)

An Oakland police officer pauses after being hit in the face with paint as officers advanced on Occupy protesters blocking an intersection during a May Day demonstration on May 1, 2012 in Oakland, California. (Photo by Justin Sullivan/Getty Images)

A police lieutenant swings his baton at an Occupy Wall Street activists on Tuesday, May 1, 2012 in New York. (Photo by Mary Altaffer/AP Photo)

Police confront demonstrators during May Day protests on Tuesday, May 1, 2012 in Oakland, Calif. (Photo by Marcio Jose Sanchez/AP Photo)

Police officers detain an activist from the women's rights group FEMEN during a protest against the arrest of their Tunisian member named Amina, in front of Tunisia's Ministry of Justice in Tunis May 29, 2013. (Photo by Anis Mili/Reuters)