U.S. President Donald Trump's recent assertion that U.S. troops should respond to rock-throwing migrants — a hypothetical scenario — as if they were armed has sparked a debate about the appropriate use of force.
Nigerian troops swiftly used Trump's comments about the migrants as justification for a deadly crackdown on demonstrators over the weekend.
From the Gaza Strip to Africa and Europe, security forces have faced stone throwers in very different ways, from firing live rounds to limiting themselves to non-lethal means.
A 1990 UN document calls on law enforcement officials to show maximum restraint and to use firearms only in cases in which an "imminent threat of death or serious injury" is identified.
These standards have been interpreted differently around the world.
Last week, Trump called attention to a migrant caravan of several thousand Central Americans making their way toward the U.S. border. It is a largely peaceful procession, though some migrants in one caravan clashed with Mexico police, hurling stones.
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Although the caravan is still some 1,200 kilometers (800 miles) from the border, Trump has mobilized troops and declared that if U.S. soldiers face rock-throwing migrants, they should react as though the rocks were "rifles."
Trump later said he was merely calling for the arrests of stone throwers.
But following Trump's comments, Nigeria's military sent out a tweet that appeared to use his words as justification for shooting and killing Shiite protesters. It later removed the tweet.
Omar Shakir, the Israel-Palestine director of the international group Human Rights Watch, said he fears Trump's comments could encourage other forces to loosen their rules of engagement.
"Trump's brazen, inflammatory statements, days before U.S. midterm elections, have already been seized on by rights abusers to justify more expansive open fire standards," he said.
Here is a look at how countries around the world respond to stone throwers.
Israeli forces have been confronting Palestinian stone throwers in the West Bank and Gaza Strip for decades. Israeli tactics have evolved over the years, particularly with the increased use of what are presented as non-lethal crowd-dispersal tools such as tear gas and rubber bullets.
Israeli officials say that live fire is used only as a last resort, when soldiers' lives are threatened. But critics accuse Israel of unnecessarily, and perhaps illegally, using deadly force.
In recent months, for instance, over 160 Palestinians have been killed during mass protests along Gaza's border with Israel. Many have been unarmed.
Israel says threats go beyond stone throwing, and that protesters throw grenades and firebombs, or try to break through the border to attack Israeli civilians.
David Tzur, a former commander of Israel's paramilitary Border Police, said non-lethal force is sufficient in most cases, but that troops could be justified using live fire in more chaotic situations, if a moving vehicle is pelted with stones in a tense locale, for instance.
In Greece, firebombs and stone-throwing are routine occurrences at anarchist demonstrations held on most weekends. Police typically respond with tear gas and stun grenades to disperse the crowds.
In 2008, a policeman fired his gun at a group of youths in central Athens, killing a 15-year-old protester. The death sparked two weeks of riots in major cities across Greece, and the policeman was jailed for murder.
Mirgrants in Europe
Migrants making their way to Europe have clashed with security forces in various countries.
In Spain, migrants from Africa have on several occasions stormed across the border, assaulting police officers with acid, skin irritants and other objects.
But police are not permitted to use live ammunition and have not even used rubber bullets against migrants since a much-criticized crackdown in 2014. Spanish police did use rubber bullets last year in clashes with Catalan separatists.
Hungary, which takes one of the hardest lines against migrants, used only tear gas and water cannons in a major clash with migrants three years ago. One Syrian migrant, however, was sentenced to five years in prison on terrorism charges for entering the country illegally and throwing stones at police.
In Indian-administered Kashmir, a disputed territory divided between India and Pakistan, protesters have long viewed stone throwing as legitimate protest against Indian rule.
India has often responded with tough measures, including live fire and metal pellets that have killed, maimed or blinded hundreds of people over the last decade. India says its troops are in life-threatening situations that justify the heavy use of force.
Protesters caught throwing stones at soldiers and police — often identified through video recordings of demonstrations — are usually accused of attempting to murder government officials, a charge that carries long imprisonment. Many stone throwers have been shot dead by soldiers.
Rebels have been fighting Indian control since 1989. Nearly 70,000 people have been killed in the uprising and the ensuing Indian military crackdown.