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A law enforcement agency (LEA) is any government agency responsible for law enforcement within a specific jurisdiction through the employment and deployment of law enforcement officers and their resources. The most common type of law enforcement agency is the police, but various other forms exist as well, including agencies that focus on specific legal violation, or are organized and overseen by certain authorities. They typically have various powers and legal rights to allow them to perform their duties, such as the power of arrest and the use of force.

LEAs which have their ability to apply their powers restricted in some way are said to operate within a jurisdiction.

Jurisdictions are traditionally restricted to a geographic area and territory. LEA might be able to apply its powers within a state (e.g. the National Police for the entirety of France), within an administrative division (e.g. the Ontario Provincial Police for Ontario, Canada), within a division of an administrative division (e.g. the Miami-Dade Police Department for Miami-Dade County, Florida, United States), or across a collection of states typically within an international organization or political union (e.g. Europol for the European Union).

Sometimes, an LEA's jurisdiction is determined by the type of violation committed relative to the laws the LEA enforces, who or what the violation affects, or the seriousness of the violation. For example, in the United States, the Postal Inspection Service primarily investigates crimes affecting or misusing the services of the United States Postal Service, such as mail and wire fraud. If, hypothetically, a Postal Inspection Service investigation uncovered tobacco smuggling, the Bureau of Alcohol, Tobacco, Firearms and Explosives would be involved, but the Drug Enforcement Administration would not, as even though they investigate drug smuggling, their jurisdiction does not cover specifically tobacco smuggling. In other cases, an LEA's involvement is determined based on whether their involvement is requested; the Australian Federal Police, for instance, has jurisdiction over all of Australia, but usually takes on complex serious matters referred to it by another agency, and the agency^[which?] will undertake its own investigations of less serious or complex matters by consensus.^[1][2]

LEA jurisdictions for a country and its divisions can typically be at more than one level. The United States has five basic tiers of law enforcement jurisdiction: federal, state, county, municipality, and special jurisdiction (tribal, airport, transit, railroad, etc.). Only the municipal, county, and state levels are involved in direct policing (i.e. uniformed officers with marked cars and regular patrols), and these can still depend on each agency's role and function. As an example for the American tiers, the Chicago Police Department has jurisdiction over Chicago, but not necessarily the rest of Cook County; while the Cook County Sheriff's Office has jurisdiction over Cook County, for the most part they patrol unincorporated area and operate Cook County Jail, and leave municipalities to municipal police departments; and the rest of Illinois, primarily its state highways, are under the jurisdiction of the Illinois State Police. All three technically have overlapping jurisdictions, and though their regular duties are fairly different and they typically avoid each other's responsible areas (the Cook County Sheriff's Office typically avoids patrolling Chicago unless it is for penal or court-related duties), they are still capable of assisting each other if necessary, usually in the form of higher-tier agencies assisting lower-tier agencies.

In some countries, national or federal police may be involved in direct policing as well, though what they focus on and what their duties are may vary. In Brazil, there are five federal police forces with national jurisdiction—the Federal Police of Brazil, the Federal Highway Police, the Federal Railroad Police, the Federal Penal Police, and the National Public Security Force—but the Highway Police, Railroad Police, and Penal Police are restricted to specific area jurisdictions (the Brazilian Highway System, railways, and prisons respectively) and do not investigate crimes, the Federal Police performs various police duties across the country and does investigate crimes, while the National Public Security Force is a rapid reaction force deployed to assist state authorities on request.

Often, a LEA's jurisdiction will be geographically divided into operations areas for administrative and logistical efficiency reasons. An operations area is often called a command,^[3] division, or office.^[4][5] Colloquially, they are known as beats.

While the operations area of a LEA is sometimes referred to as a jurisdiction, any LEA operations area usually still has legal jurisdiction in all geographic areas the LEA operates, but by policy and consensus the operations area does not normally operate in other geographical operations areas of the LEA. For example, since 2019 the frontline or territorial policing of the United Kingdom's Metropolitan Police has been divided into 12 Basic Command Units, each consisting of two, three, or four of the London boroughs,^[6] while the New York City Police Department is divided into 77 precincts.^[7]

Sometimes, the one legal jurisdiction is covered by more than one LEA, again for administrative and logistical efficiency reasons, or arising from policy, or historical reasons. In England and Wales, LEAs called constabularies have jurisdiction over their respective areas of legal coverage, but they do not normally operate out of their areas without formal liaison between them. The primary difference between separate agencies and operational areas within the one legal jurisdiction is the degree of flexibility to move resources between versus within agencies. When multiple LEAs cover the one legal jurisdiction, each agency still typically organizes itself into operations areas. In the United States, within a state's legal jurisdiction, county and city LEAs do not have full legal jurisdictional flexibility throughout the state, and this has led in part to mergers of adjacent police agencies.

Jurisdictionally, there can be an important difference between international LEAs and multinational LEAs, even though both are often referred to as "international", even in official documents. An international law enforcement agency has jurisdiction and or operates in multiple countries and across state borders, such as Interpol. A multinational law enforcement agency will typically operate in only one country, or one division of a country, but is made up of personnel from several countries, such as the European Union Police Mission in Bosnia and Herzegovina.^[8][9] International LEAs are typically also multinational,^[10] but multinational LEAs are typically not international. LEAs which operate across a collection of countries tend to assist in law enforcement activities, rather than directly enforcing laws, by facilitating the sharing of information necessary for law enforcement between LEAs within those countries.

Within a country, the jurisdiction of law enforcement agencies can be organized and structured in a number of ways to provide law enforcement throughout the country. A law enforcement agency's jurisdiction can be for the whole country or for a division or sub-division within the country.

When a LEA's jurisdiction is for the whole country, it is usually one of two broad types, either federal or national.

When the country has a federal constitution, an LEA responsible for the entire country is referred to as a federal law enforcement agency.

The responsibilities of a federal LEA vary from country to country. Federal LEA responsibilities are typically countering fraud against the federation, immigration and border control regarding people and goods, investigating currency counterfeiting, policing of airports and protection of designated national infrastructure, national security, and the protection of the country's head of state and of other designated very important persons, such as the U.S. Secret Service^[11] or the U.S. Department of State Diplomatic Security Service.

A federal police agency is a federal LEA that also has the typical police responsibilities of social order and public safety as well as federal law enforcement responsibilities. However, a federal police agency will not usually exercise its powers at a divisional level. Such exercising of powers is typically specific arrangements between the federal and divisional governing bodies.

Examples of federal law enforcement agencies include the:

• Argentine Federal Police (Argentina)
• Australian Federal Police (Australia)
• Federal Police of Brazil (Brazil)
• Royal Canadian Mounted Police (Canada)
• Bundespolizei (Germany)
• Mexican Federal Police (Mexico)
• Federal Bureau of Investigation, Federal Protective Service, United States Park Police (United States)
• Central Bureau of Investigation (India)

A federated approach to the organization of a country does not necessarily^[12] indicate the nature of the organization of law enforcement agencies within the country. Some countries, such as Austria and Belgium, have a relatively unified approach to law enforcement, but still have operationally separate units for federal law enforcement and divisional policing. The United States has a highly fractured approach to law enforcement agencies generally, and this is reflected in American federal law enforcement agencies.

In a federation, there will typically be separate LEAs with jurisdictions for each division within the federation. A federal LEA will have primary responsibility for laws which affect the federation as whole, and which have been enacted by the governing body of the federation.

Members of a federal LEA may be given jurisdiction within a division of a federation for laws enacted by the governing bodies of the divisions either by the relevant division within the federation, or by the federation's governing body. By way of example, the Australian Federal Police is a federal agency and has the legal power to enforce the laws enacted by any Australian state, but will generally only enforce state law if there is a federal aspect to investigate.^[13]

Typically, federal LEAs have relatively narrow police responsibilities, the individual divisions within the federation usually establish their own police agencies to enforce laws within the division. However, in some countries federal agencies have jurisdiction in divisions of the federation. This typically happens when the division does not have its own independent status and is dependent on the federation. The Royal Canadian Mounted Police (RCMP) is one such federal agency that also acts as the sole police agency for Canada's three territories, Northwest Territories, Nunavut, and Yukon.^[14] This is a direct jurisdictional responsibility and is different from the situation when a governing body makes arrangements with another governing body's LEA to provide law enforcement for its subjects.

In federal polities, actions that violate laws in multiple geographical divisions within the federation are escalated to a federal LEA. In other cases, specific crimes deemed to be serious are escalated; in the United States, the FBI has responsibility for the investigation of all kidnapping cases, regardless of whether it involves the crossing of state lines.^[15] Some countries provide law enforcement on land and in buildings owned or controlled by the federation by using a federal LEA; for example, the U.S. Department of Homeland Security^[16] is responsible for some aspects of federal property law enforcement

Typically, LEAs working in different jurisdictions which overlap in the type of law non-compliance actively establish mechanisms for cooperation, establish joint operations and joints task forces.^{[17][18][19][20]} Often, members of a LEA working outside of their normal jurisdiction on joint operations or task force are sworn in as special members of the host jurisdiction.

A national law enforcement agency is a LEA in a country which does not have divisions capable of making their own laws. A national LEA has the combined responsibilities that federal LEAs and divisional LEAs would have in a federated country. National LEAs are usually divided into operational areas.

To help avoid confusion over jurisdictional responsibility, some federal LEAs, such as the U.S. FBI, explicitly advise that they are not a national law enforcement agency.^[17]

A national police agency is a national LEA that also has the typical police responsibilities of social order and public safety as well as national law enforcement responsibilities. Examples of countries with non-federal national police agencies are New Zealand, Italy, Indonesia, France, Ireland, Japan, Netherlands, Malaysia, the Philippines, and Nicaragua.

State police, provincial police, or regional police are a type of subnational territorial police force found in nations organized as federations, typically in North America, South Asia, and Oceania, because each of their state police are mostly at country level. These forces typically have jurisdiction over the relevant sub-national jurisdiction, and may cooperate in law enforcement activities with municipal or national police where either exist.

LEAs can be responsible for the enforcement of laws affecting the behavior of people or the general community (e.g. New York City Police Department), the behavior of commercial organizations and corporations (e.g. Australian Securities and Investments Commission), or for the interests of the country as a whole (e.g. United Kingdom's His Majesty's Revenue and Customs).

Many law enforcement agencies are police agencies that have a broad range powers and responsibilities. Police agencies, however, also often have a range of responsibilities not specifically related to law enforcement. These responsibilities relate to social order and public safety. While this understanding of policing, being more encompassing than just law enforcement has grown with and is commonly understood by society, it is recognized formally by scholars and academics.^[21] A police agency's jurisdiction for social order and public safety will normally be the same as its jurisdiction for law enforcement.

Military organizations often have law enforcement units. These units within armed forces are generally referred to as military police. This may refer to:

• a section of the military solely responsible for policing the armed forces (referred to as provosts)
• a separate section of the armed forces responsible for policing in the armed forces and in the ministry of defence (such as the Żandarmeria Wojskowa)
• a section of the military solely responsible for policing the civilian population (such as the Romanian Gendarmerie)
• the preventative police, with military status, of a state (such as the Brazilian Military Police)

The exact usage and meaning of the terms military police, provost, security forces, and gendarmerie vary from country to country.

Non-military law enforcement agencies are sometimes referred to as civilian police, but usually only in contexts where they need to be distinguished from military police. However, they may still possess a military-like structure and protocol.

In most countries, the term law enforcement agency when used formally includes agencies other than only police agencies. The term law enforcement agency is often used in the United States to refer to police agencies, however, it also includes agencies with peace officer status or agencies which prosecute criminal acts. A county prosecutor or district attorney is considered to be the chief law enforcement officer of a county.

Other responsibilities of LEAs are typically related to assisting subjects to avoid non-compliance with a law, assisting subjects to remain safe and secure, assisting subjects after a safety impacting event. These include:

• policing^[21]
  • social order
    • public incident mediation
    • pre-empting anti-social behaviour
    • dangerous event public logistics
  • public safety
    • general search and rescue
    • crowd control
• regulation
• services and facilities
• disaster victim identification
• education and awareness campaigns
  • victim prevention and avoidance
  • law compliance
  • public safety

Many LEAs have administrative and service responsibilities, often as their major responsibility, as well as their law enforcement responsibilities. This is typical of agencies such as customs or taxation agencies, which provide services and facilities to allow subjects to comply with relevant laws as their primary responsibilities.

Private police are law enforcement bodies that are owned or controlled by non-governmental entities. Private police are often utilized in places where public law enforcement is seen as being under-provided. For example, the San Francisco Patrol Special Police was formed to increase security in San Francisco during the California gold rush, and presently still exists to protect locations on the request of private clients.

In Canada and the United States, many railroad companies have private railroad police. Examples include the BNSF Police Department, Canadian National Police Service, Canadian Pacific Kansas City Police Service, Union Pacific Police Department, etc. The Canadian National Police Service and Canadian Pacific Kansas City Police Service operate in both countries while the others operate only in the US.

Many LEAs are also involved in the monitoring or application of regulations and codes of practice. See, for example, Australian Commercial Television Code of Practice, building code, and code enforcement. Monitoring of the application of regulations and codes of practice is not normally considered law enforcement. However, the consistent non-compliance by a subject with regulations or codes of practice may result in the revocation of a license for the subject to operate, and operating without a licence is typically illegal. Also, the failure to apply codes of practice can impact other subjects' safety and life, which can also be illegal.

A LEA can be responsible for enforcing secular law or religious law such as Sharia or Halakha. The significant majority of LEAs around the world are secular, and their governing bodies separating religious matters from the governance of their subjects. Religious law enforcement agencies, such as Saudi Arabia's Mutaween or Iran's Guidance Patrol, exist where full separation of government and religious doctrine has not occurred, and are generally considered police agencies, typically religious police, because their primary responsibility is for social order within their jurisdiction and the relevant social order being highly codified as laws.

Often, a LEA will have a specific internal unit to ensure that the LEA is complying with relevant laws such as the U.S. Federal Bureau of Investigation's Office of Professional Responsibility.^[12] In some countries and regions, specialised or separate LEAs are established to ensure that other LEAs comply with laws and investigate potential violations of laws by law enforcers, like the New South Wales Independent Commission Against Corruption or the Ontario Special Investigations Unit.^[22][23][24]

Typically, a LEA is established and constituted by the governing body it is supporting, and the personnel making up the LEA are from the governing body's subjects.

For reasons of either logistical efficiency or policy, some divisions with a country will not establish their own LEAs but will instead make arrangements with another LEA, typically from the same country, to provide law enforcement within the division. For example, the Royal Canadian Mounted Police (RCMP) is a federal agency and is contracted by most of Canada's provinces and many municipalities to police them, even though law enforcement in Canada is constitutionally a divided responsibility. This arrangement has been achieved by formal agreement between those provinces and municipalities and the federal government, and reduces the number of agencies policing the same geographical area.^[25]

In circumstances where a country or division within a country is not able to establish stable or effective LEAs, typically police agencies, the country might invite other countries to provide personnel, experience, and organisational structure to constitute a LEA, such as the Regional Assistance Mission to the Solomon Islands which has a Participating Police Force^[26] working in conjunction with the Solomon Islands Police Force. In circumstances where the United Nations is already providing an administrative support capability within the country, the United Nations may directly establish and constitute a LEA on behalf of the country, as occurred under the United Nations Transitional Administration in East Timor, which operated in Timor-Leste from 1999 to 2002;^[27] related is the United Nations Police, which helps provide law enforcement during United Nations peacekeeping missions.

To enable a LEA to prevent, detect, and investigate non-compliance with laws, the LEA is endowed with powers by its governing body which are not available to non LEA subjects of a governing body. Typically, a LEA is empowered to varying degrees to:

• collect information about subjects in the LEA's jurisdiction
• intrusively search for information and evidence related to the non-compliance with a law
• seize evidence of non-compliance with a law
• seize property and assets from subjects
• direct subjects to provide information related to the non-compliance with a law
• arrest and detain subjects, depriving them of their liberty, but not incarcerate subjects, for alleged non-compliance with a law
• lawfully deceive subjects

These powers are not available to subjects other than LEAs within the LEA's jurisdiction and are typically subject to judicial and civil overview.

Usually, these powers are only allowed when it can be shown that a subject is probably already not complying with a law. For example, to undertake an intrusive search, typically a LEA must make an argument and convince a judicial officer of the need to undertake the intrusive search on the basis that it will help detect or prove non-compliance with a law by a specified subject. The judicial officer, if they agree, will then issue a legal instrument, typically called a search warrant, to the LEA, which must be presented to the relevant subject if possible.

Subjects who do not comply with laws will usually seek to avoid detection by a LEA. When required, in order for the LEA to detect and investigate subjects not complying with laws, the LEA must be able to undertake its activities secretly from the non-complying subject. This, however, may require the LEA to explicitly not comply with a law other subjects must comply with. To allow the LEA to operate and comply with the law, it is given lawful exemption to undertake secret activities. Secret activities by a LEA are often referred to as covert operations.

To deceive a subject and carry out its activities, a LEA may be lawfully allowed to secretly:

• Create and operate false identities and personalities and organisations, often referred to as undercover operations or assumed identities, e.g. the Australian Federal Police by virtue of Part 1AC of the Crimes Act 1914.^[28]
• Allow and assist the illicit movement of licit and illicit substances and wares, sometimes partially substituted with benign materials, often referred to as controlled operations, e.g. Australia's LEAs by virtue of Part 1AB of the Crimes Act 1914.^[29]
• Listen to and copy communications between subjects, often referred to as telecommunications interception or wiretapping when the communication medium is electronic in nature, e.g. the U.S. Federal Bureau of Investigation by virtue of United States Code 18 Title 18 Part I Chapter 119 Section 2516.^[30]
• Intrusively observe, listen to, and track subjects, often referred to as technical operations, e.g. Australian LEAs by virtue of the Surveillance Devices Act 2004.^[31]

to typically collect information about and evidence of non-compliance with a law and identify other non-complying subjects.

Lawful deception and use of law exemption by a LEA is typically subject to very strong judicial or open civil overview. For example, the Australian Federal Police's controlled operations are subject to open civil review by its governing body, the Parliament of Australia.^[32][33]

Law enforcement agencies have other exemptions from laws to allow them to operate in a practical way. For example, many jurisdictions have laws which forbid animals from entering certain areas for health and safety reasons. LEAs are typically exempted from these laws to allow dogs to be used for search and rescue, drug search, explosives search, chase and arrest, etc.^[34] This type of exemption is not unique to LEAs. Sight assist dogs are also typically exempted from access restrictions. Members of LEAs may be permitted to openly display firearms in places where this is typically prohibited to civilians, violate various traffic laws in the course of their duties, or detain persons against their will.

Interpol is an international organisation and is essentially stateless, but must operate from some physical location. Interpol is protected from certain laws of the country where it is physically located.^[35]

• List of anti-corruption agencies
• Code enforcement
• List of law enforcement agencies grouped by sub category
  • List of protective service agencies
  • List of secret police organizations
  • List of specialist law enforcement agencies
• Outline of law enforcement
• Specialist law enforcement agency
• Traffic police
• State police
• Sheriff
• Police
• Police foundation

• Berlin: Metropolis of crime 1918 - 1933 Part 1, Part 2 (warning: graphic depiction of murder and other violence), a Deutsche Welle English television documentary comprehensively depicting a major European police force and its methods, investigations, and political activities during the early 20th century