Serbian police officers of the Special Anti-Terrorist Unit pose for a picture in their base outside Belgrade October 8, 2014. When the killing of an unarmed black teenager by a white policeman in Ferguson, Missouri, in August sparked sometimes violent protests, the response of police in camouflage gear and armoured vehicles wielding stun grenades and assault rifles seemed more like a combat operation than a public order measure. Some U.S. police departments have recently acquired U.S. military-surplus hardware from wars abroad, but there are many law enforcers around the world whose rules of engagement also allow the use of lethal force with relatively few restrictions. But for every regulation that gives police wide scope to use firearms, there is another code that sharply limits their use. In Serbia, police may use measures ranging from batons to special vehicles, water cannon and tear gas on groups of people who have gathered illegally and are behaving in a way that is violent or could cause violence, but they may use firearms only when life is endangered. (Photo by Marko Djurica/Reuters)

An Iraqi special forces soldier wears a rose in his body armor as troops move from the Yarmouk neighborhood to take another district from Islamic State militant control in Mosul, Iraq, Wednesday, April 12, 2017. (Photo by Maya Alleruzzo/AP Photo)

Staff of a boat restaurant on the Taedong River line up at the entrance as they wait to greet customers Sunday, June 18, 2017, in Pyongyang, North Korea. The boat is berthed along the river, which is the fifth longest river on the Korean Peninsula and runs through the country's capital, Pyongyang. (Photo by Wong Maye-E/AP Photo)

A young boy plugs his ears as his sister (C) and nanny (L) watch from Gravelly Point Park as planes land at Reagan National Airport in Arlington, Virginia on June 29, 2017. President Donald Trump' s travel ban on people from six mostly Muslim countries will come into force late Thursday, as controversy swirls over who qualifies for an exemption based on family ties. (Photo by Jim Watson/AFP Photo)

George Harrison of the Beatles sits cross-legged with his musical mentor, Ravi Shankar of India, a sitar virtuoso, in Los Angeles, August 3, 1967, as Harrison explains to newsmen that Shankar is teaching him to play the sitar, a 25-stringed guitar-like instrument. Harrison said “Indian music makes God come through in a spiritual way”. (Photo by AP Photo)

At a beauty contest to select the nation's Queen of Height during the first national convention of Tall People's Clubs in New York on July 29, 1949, little Charlie Young, only three feet, eleven inches tall, acting as judge, had a tough time making up his mind for the choice. The national minimum height requirement for women members is 5 feet 10 inches, and for men, 6 feet. (Photo by Robert Kradin/AP Photo)

Eight-year-old Lactatia a.k.a. Nemis Quinn Mélançon Golden gets a makeover by Ginger Minj during RuPaul's DragCon NYC 2017 at The Jacob K. Javits Convention Center on September 9, 2017 in New York City. (Photo by Santiago Felipe/Getty Images)

Bride Katty Malang Mikunug with friends, takes a photo before the wedding on October 21, 2017 in Saguiaran in Lanao del Sur, southern Philippines. Paulo Mamayo Ambor, 22, a resident of Marawi who got displaced by the fighting between government troops and IS-inspired militants, weds Katty Malang Mikunug, 22, a resident of an adjacent town in Saguiaran. Philippines President Rodrigo Duterte declared Marawi liberated, following the death of Abu Sayyaf leader Isnilon Hapilon and one of the Maute brothers, Omar Maute, after nearly five months of fierce urban battle inside the besieged city. The fighting started May 23, and left more than 1,000 people dead, whilst displacing at least 400,000 people. (Photo by Jes Aznar/Getty Images)