(Reuters) - U.S. police are under pressure not only for the killing of an unarmed teenager in Ferguson, Missouri, for which a grand jury decided on Monday not to indict the police officer, but also for the military-style response to the sometimes violent protests that followed.
The sight in August of police in camouflage gear, backed up by armored vehicles and brandishing assault rifles, was a reminder that some U.S. police departments have recently acquired U.S. military-surplus hardware from wars abroad.
Yet many other law enforcers around the world have rules of engagement that allow lethal force to be used relatively freely.
Venezuela's Interior Ministry decrees that, when peaceful methods of resolution have failed, police must warn violent demonstrators that there will be a “progressive, differentiated use of force”. While no firearms must be carried for peaceful demonstrations, when things turn violent, the emphasis is on avoiding harm to children, pregnant women and the elderly.
Afghanistan's police, often themselves the target of armed attacks, are officially authorized to respond with weapons "and explosives", albeit only after other methods have failed, and no fewer than six warnings have been issued.
But for every regulation that gives police wide scope to use firearms, there is another code that sharply limits their use.
Mexican and Indian riot police follow defined escalation protocols that go from verbal warnings to physical constraint, tear gas, water cannon or pepper spray, rubber bullets or baton rounds, and then use of firearms.
Yet while Mexican police commanders can decide when to escalate, India's Rapid Action Force requires approval from an on-the-spot magistrate for each new step.
Many countries spell out that any use of firearms is a last resort, though this can be defined many ways.
Britain, Serbia, Bosnia and the Philippines allow guns to be fired only if a life is at risk. Britain stands out for its insistence that "individual officers are accountable and responsible for any use of force and must be able to justify their actions in law".
Many West European countries, meanwhile, allow firearms to be used "where necessary" to detain suspects or to prevent a serious crime.
Police at the extraterritorial United Nations buildings in Geneva are not subject to Swiss law but still conform to local police rules. These rules, like those governing police in Italy, Austria, Belgium and Bosnia, specify that the use of force must be "proportionate".
In Belgium, human rights monitors say, this means firearms can never be used for crowd control.
Malaysia's Federal Reserve Unit, the main riot force, is permitted to use firearms only when protesters are using them, but it is in a fortunate position. Its deputy superintendent, Kulwant Singh, says that "firearms have not been used in the 59 years since the FRU was formed".
Reporting by Reuters photographers and bureaux around the world; Editing by Gareth Jones