JERUSALEM – President Donald Trump's assertion that stones thrown by Latin American protesters at American troops should be treated as "rifles" has sparked debate about the appropriate response to rock-throwing crowds — particularly after Nigerian troops appeared to use his comments as justification for a deadly crackdown on demonstrators over the weekend.
From the Gaza Strip to Africa to Europe, security forces have long dealt with stone throwers, albeit in very different ways.
Israel has killed dozens of Palestinian stone-throwers over the decades, saying that rocks constituted a threat to the lives of its soldiers. In Greece, the killing of a single stone-thrower by a rogue policeman a decade ago set off weeks of riots across the country.
A 1990 U.N. document, "Basic Principles on the Use of Force and Firearms by Law Enforcement Officials," is widely seen as setting the international standard for the use of force in policing environments, according to Omar Shakir, the Israel and Palestine director for Human Rights Watch.
It calls on law-enforcement agencies 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 took aim at a migrant caravan of several thousand Central Americans making their way toward the U.S. border. 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.
Shakir 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 "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 the crowds are being incited by the Hamas militant group, and the threats go far beyond stone throwing. It says protesters are throwing grenades and firebombs and trying to infiltrate the border to attack Israeli civilians.
David Tzur, a former commander of Israel's Border Police, a paramilitary force often used in riot-control situations, said shooting to kill is to be avoided as much as possible and that non-lethal force is sufficient in most cases. But he said 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.
He said he expected U.S. troops to do everything possible to avoid deadly force, since doing so escalates the situation. "My guess is they won't be eager to start shooting," he said.
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 rogue 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.
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, pelting policemen 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.
French regulations allow police officers to use force as "legitimate defense" against aggression. But any use of force must be proportionate, immediate and necessary.
Police do not consider "normal" stones to be life threatening, so live fire is normally prohibited. In "exceptional" cases, such as a boulder being hurled at forces, live fire could be prohibited.
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 a legitimate form of 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 stone throwing at soldiers and police — often identified through video recordings of demonstrations — are usually accused of attempting to murder government functionaries, a charge that invokes long imprisonment if convicted. 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.
Aijaz Hussain in Srinigar, India; Elena Becatoros in Athens; Thomas Adamson in Paris; Pablo Gorondi in Budapest, Hungary; Joseph Wilson in Barcelona, Spain, and Aron Heller in Jerusalem contributed reporting.