A protester dressed as a clown holds an umbrella over a Swiss police officer on a motorbike during a May Day demonstration in Zurich, Switzerland on May 1, 2017. (Photo by Arnd Wiegmann/Reuters)

School leavers celebrate their graduation in Moscow's Red Square in Moscow, Russia on June 20, 2019. (Photo by Artyom Geodakyan/TASS)

A “caixer” (horse rider) rears up on his horse surrounded by a cheering crowd during the traditional “Jaleo” at the Sant Antoni Festival in Es Castell, Balearic Islands, Spain on July 27, 2019. (Photo by Matthias Oesterle/Zuma Press/Picturedesk.com)

A demonstrator is detained during May Day rallies in Santiago May 1, 2013. (Photo by Ivan Alvarado/Reuters)

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)

A devotee in trance mimics a beast during a religious tattoo festival at Wat Bang Phra monastery, where devotees believe that their tattoos have mystical powers, in Nakhon Pathom province, Thailand, March 16, 2019. (Photo by Athit Perawongmetha/Reuters)

Militia members march in formation past Tiananmen Square during the military parade marking the 70th founding anniversary of People's Republic of China, on its National Day in Beijing, China on October 1, 2019. (Photo by Thomas Peter/Reuters)

American singer-songwriter Taylor Swift eyes are caught in a photographer's flash as she arrives on the red carpet for the “Billboard Women in Music” event in Los Angeles, California, U.S., December 12, 2019. (Photo by Mike Blake/Reuters)