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)

Garbage pickers collect ride on donkey cart while looking for recyclable materials at a rubbish dump in the outskirts of Baghdad, Iraq, August 23, 2016. Despite its huge untapped oil and gas reserves and steadily rising oil output and revenue, 23 percent of the population live below the poverty line, according to the Ministry of Planning. (Photo by Khalid al Mousily/Reuters)

Young children at a Bristol, Great Britain health centre unsure of the benefits of sun-lamps and the special glasses that must be worn, July 1948. The health centre was part of the newly introduced free National Health Service. (Photo by Popperfoto/Getty Images)

An undated handout photo made available by the Zerynthia Association shows the pupa of an amicta moneiba, a recently discovered species of moth endemic to La Gomera and El Hierro islands in the Canary Islands, Spain (issued 01 July 2020), as those two islands pulled apart from the rest of the Canary Islands 2.5 million years ago. The Institute of Evolutionary Biology of the Spanish National Research Council (CSIC) and the Zerynthia Association have recently discovered two new moth species in El Hierro and La Gomera. (Photo by Yeray Monasterio/Zerynthia/EPA/EFE)

A competition, now in its 43rd year, dedicated to showcasing the beautiful and bizarre as seen under a light microscope attracted over 2,000 entries from 88 countries. Here: Honorable Mention by Emre Can Alagöz, Istanbul, Turkey: The eyes of a jumping spider, magnified 6x. (Photo by Emre Can Alagöz/2017 Nikon Small World Photomicrography Competition)

Members of the Hitler Youth who are trained to report airstrikes repaining their bicycles. Published by: “Die Sirene”. 1942. (Photo by Herbert Hoffmann/Ullstein Bild via Getty Images)

Frances Fowler leads the Bowie VFD Marching Thoroughbreds in the Bowie 4th of July Parade in Bowie, Md., on July 4, 1976. (Photo by James M. Thresher/The Washington Post via Getty Images)

A man reacts as he tries to extinguish a burning Christmas tree at Festival Walk mall in Kowloon Tong, Hong Kong, November 12, 2019. Anti-government protesters smashed windows and set fires in the mall on Tuesday, including to a big Christmas tree. (Photo by Thomas Peter/Reuters)