Members of Belgium’s special forces at their headquarters in central Brussels. (Yves Herman/Reuters)

In 1993 the Justice Department installed the 1033 program as a way to help law enforcement agencies counter drug activities during the United States’ “war on drugs.”  In 1997, the boundaries of law enforcement expanded after Congress passed the National Defense Authorization Act, granting police and other agencies the right to obtain weaponry for specific law enforcement purposes that would help in making arrests. Many U.S. police departments have since acquired surplus U.S. military hardware: armored vehicles, military-grade weaponry. According to Reuters, since 1996 the Defense Department has transferred $4.3 billion in military equipment to local and state police through the 1033 program. And after 9/11, the Department of Homeland Security allowed local law enforcement to inherit a surplus of military weaponry from wars abroad through federal funds to counter terrorism.

The recent clashes between heavily armed law enforcement and protesters in the wake of a police officer killing of unarmed black teenager Michael Brown in Ferguson, Mo., have reignited the discussion surrounding the militarization of American police forces. The rules of engagement for police or paramilitary forces abroad allows the use of lethal force using military-grade gear with relatively few restrictions. But with that is a code of conduct, a set of rules, that sharply regulates the wide latitude of law enforcement, and puts into a place a system of accountability.

Human rights monitors say police in Belgium are legally entitled to use proportionate force, after a warning, where there is no other means to achieve a legitimate objective. Police may use firearms in self-defense, to confront armed perpetrators, or in defense of persons or key facilities, but never for crowd control. In Afghanistan, “the police can use weapons or explosives against a group of people only if they it has … disturbed security by means of arms, and if the use of other means of force … has proved ineffective.” And Afghan police are required to give no fewer than six warnings — three verbal and three warning shots — before using force in this situation. In India, the Rapid Action Force (RAF) are called on for violent disorder that the police are unable to contain. They require an on-the-spot magistrate’s consent and must issue a warning before each escalation of the use of force, from verbal warning to water cannon and tear gas, then to rubber bullets or baton rounds, and then to firearms. Britain’s law states that “lethal or potentially lethal force should only be used when absolutely necessary in self-defense, or in the defense of others against the threat of death or serious injury.” In Italy, police and the paramilitary Carabinieri follow the same guidelines, which say that the use of weapons is allowed only in the line of duty, when it is an “unavoidable necessity to overcome resistance, stop violence or prevent a [serious] crime,” and that the response must be proportionate to the situation.

The series below takes a closer look at law enforcement around the world and their respective tactics.

Portions of this text were contributed by Reuters.

AFGHANISTAN: From left, officers Habib, 21, Sayed Rahman, 22, Mohammad Nabi, 22, Momin Khan, 22, and Abdul Ali, 25, in their anti-riot gear at their base in Kabul. (Omar Sobhani/Reuters)

INDIA: A Mumbai police constable stands guard next to an armored vehicle outside the police commissioner’s office. (Danish Siddiqui/Reuters)

BRITAIN: Police constable Ben Sinclair wears his Metropolitan Police uniform with high visibility jacket in London. (Paul Hackett/Reuters)

BRITAIN: Police constables Ben Sinclair and Karen Spencer wearing their Metropolitan Police beat uniforms, in London. (Paul Hackett/Reuters)

MALAYSIA: Public order police, the Federal Reserve Unit, in riot control equipment at their headquarters in Kuala Lumpur. In Malaysia, the FRU officers are only permitted to use firearms in cases where the protesters are using firearms. Firearms have not been used in the 59 years since the FRU was formed. (Olivia Harris /Reuters)

SERBIA: Gendarmerie officers inside their base in Belgrade. 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. (Marko Djurica/Reuters)

ITALY: Carabinieri pose in front of St. Peter’s Basilica as a Carabinieri helicopter flies overhead, in Rome. (Alessandro Bianchi/Reuters)

BOSNIA: Members of Special Police Support Unit in front of their base in central Bosnian town of Zenica. (Dado Ruvic/Reuters)

SERBIA: Officers of the Special Anti-Terrorist Unit in their base outside Belgrade. (Marko Djurica/Reuters)

PHILIPPINES: National police bomb squad members with a bomb scanner and bomb suit at a police station in Manila. In the Philippines, the use of extreme force against a suspect is allowed only if the police officer’s life or that of the victim (of the suspect) is in imminent danger. (Romeo Ranoco/Reuters)

VENEZUELA: National police officers Bello, right, and Bogado with their riot equipment, next to a mannequin in uniform during a government Christmas fair in Caracas November 13, 2014. In Venezuela, no firearms are to be carried or used for control of peaceful demonstrations. When there is a threat to order, and other methods of conflict resolution have failed, police are instructed to warn crowds or demonstrators that there will be a “progressive, differentiated use of force”. (Carlos Garcia Rawlins/Reuters)

MEXICO: Members of the Task Force for Mexico City at their base in Mexico City. (Claudia Daut/Reuters)

UNITED NATIONS: Members of the U.N. security forces in front of the European headquarters in Geneva. (Denis Balibouse/Reuters)