
U.S. police are under pressure not only for the killing of an unarmed teenager in Ferguson, Missouri - for which a grand jury decided yesterday not to indict the 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 armoured vehicles and brandishing assault rifles, was a reminder that some American 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.

Power: Serbian police officers from the Special Anti-Terrorist Unit pose for a picture in their base outside the capital city Belgrade

Armed: Belgian special forces pose for a photograph with an armoured vehicle and working dog outside their headquarters in central Brussels

Padded: A member of the Philippine National Police bomb squad stands with a bomb scanner and padded suit at a police station in Manila

Lightly armed: Afghan police officers pose with light bullet-proof vests and assault rifles outside a base in Kabul

Smart: London police constables Ben Sinclair and Karen Spencer pose for a photograph wearing their Metropolitan Police beat uniforms

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 authorised 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.

Ready for work: Members of Belgium's special forces pose for pictures at their headquarters in central Brussels

Rounds: A group of Philippine National Police Special Weapons and Tactics (SWAT) team officers pose outside a Majila police station

Transport: A Philippine National Police officer poses for a picture with a patrol segway motorcycle in front of a police station in Manila

Malaysia's public order police, the Federal Reserve Unit, are seen wearing riot control equipment at their headquarters in Kuala Lumpur

Austrians: Two Austrian police officers are seen posing in front of a water cannon in Vienna. Left, the officer wears the kind of full combat wear used in life threatening missions. Right, another officer wears clothing and body armour used in a riot situation

Rank and file: Austrian police officers pose in various uniforms in front of a water cannon at their headquarters in Vienna

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'.

Other Western European countries, meanwhile, allow firearms to be used 'where necessary' to detain suspects or to prevent a serious crime.

Shields: Members of the Task Force for Mexico City pose for a photograph in an empty car park outside their base

Lineup: Various ranks of the Task Force for Mexico City pose for a photograph with their armoured vehicles and a working dog

Venezuelan national police officers pose for a picture with their riot equipment in Caracas. They stand next to a mannequin dressed in uniform

No body armour: Members of the United Nations security forces pose in front of the U.N. European headquarters in Geneva

Tough: Afghan policeman Zabiullah, 24, poses for photo in Kabul. He wears no body armour and carries an old-fashioned assault rifle

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'.

Mighty: Members of the Bosnian Special Police Support Unit pose for photo in front of their base in the town of Zenicav

Defence brigade: India's Rapid Action Force (RAF) personnel pose for pictures inside their base camp in New Delhi

An Indian police constable stands guard next to an armoured vehicle outside the police commissioner's office in Mumbai

London police constable Ben Sinclair (left) poses for a photograph while wearing his Metropolitan Police uniform with a high visibility jacket. His colleague Karen Spencer (right) wears the more traditional Metropolitan Police beat uniform, used for daytime street patrols

Picturesque: Italian Carabinieri pose in front of St. Peter's Basilica in Rome as a Carabinieri helicopter flies overhead