Quick Summary of Mercenary

According to international law, a mercenary is a professional soldier who is hired by someone other than their own government to fight in a foreign country. For instance, a private military company may hire soldiers to protect oil fields in a foreign nation. These soldiers, known as hired guns, are not affiliated with the country’s military but are considered mercenaries. The example demonstrates the definition of a mercenary as the soldiers are employed by a private company, not their own government, to engage in combat abroad. Their motivation is financial gain rather than a cause or ideology, distinguishing them as mercenaries.

What is the dictionary definition of Mercenary?
Dictionary Definition of Mercenary

A mercenary is an individual who is employed by a party other than their own government to engage in combat in a foreign nation. These individuals are skilled experts who receive compensation for fighting on behalf of others.

Full Definition Of Mercenary

Mercenaries have been a contentious issue in international and domestic law for centuries. The use of private military contractors, often referred to as mercenaries, raises complex legal questions concerning state sovereignty, human rights, and the regulation of armed conflict. In British law, the regulation of mercenaries is influenced by a combination of domestic legislation, international treaties, and customary international law. This overview aims to provide a comprehensive analysis of the legal framework governing mercenaries in the United Kingdom.

Definition and Characteristics

The term ‘mercenary’ is defined under Article 47 of Protocol I to the Geneva Conventions of 1949. A mercenary is described as any person who:

  • Is specially recruited locally or abroad to fight in an armed conflict;
  • Does take a direct part in the hostilities;
  • Is motivated to take part in the hostilities essentially by the desire for private gain and is promised, by or on behalf of a party to the conflict, material compensation substantially more than that promised or paid to combatants of similar ranks and functions in the armed forces of that party;
  • Is neither a national of a party to the conflict nor a resident of territory controlled by a party to the conflict;
  • Is not a member of the armed forces of a party to the conflict; and
  • Has not been sent by a state which is not a party to the conflict on official duty as a member of its armed forces.

This stringent definition highlights the specific attributes that distinguish mercenaries from other combatants and private military contractors.

Historical Context

Historically, Britain has had a varied relationship with mercenaries. During the medieval and early modern periods, the use of mercenaries was commonplace. However, with the rise of the nation-state and professional national armies, the use of mercenaries began to decline. The British Foreign Enlistment Act of 1870 was one of the earliest pieces of legislation aimed at regulating British citizens’ involvement in foreign conflicts as mercenaries.

Domestic Legislation

Foreign Enlistment Act 1870

The Foreign Enlistment Act of 1870 is the primary legislation governing the participation of British citizens in foreign military services. The Act makes it an offence for British citizens to enlist in the armed forces of any foreign state at war with a state with which the United Kingdom is at peace. It also prohibits the recruitment of British citizens for such purposes within the UK. Violations of the Act can result in fines or imprisonment.

Private Security Industry Act 2001

While the Private Security Industry Act 2001 primarily regulates the domestic private security industry, it has implications for private military contractors. The Act established the Security Industry Authority (SIA), which licenses and regulates the private security industry, including companies providing private military services. However, the Act does not explicitly cover the activities of British citizens operating as mercenaries abroad, thus leaving a regulatory gap.

International Law

International Treaties

The United Kingdom is a party to several international treaties that impact the regulation of mercenaries. Notably, the UK has ratified the Geneva Conventions and their Additional Protocols, which include provisions related to the treatment of mercenaries. However, the UK is not a signatory to the International Convention against the Recruitment, Use, Financing, and Training of Mercenaries, adopted by the United Nations in 1989. This Convention seeks to criminalize the activities of mercenaries and establish international cooperation in preventing their use.

Customary International Law

Customary international law also plays a role in the regulation of mercenaries. Customary law, derived from consistent state practice and opinio juris (the belief that an action is carried out as a legal obligation), prohibits the recruitment and use of mercenaries in armed conflicts. The principle of state sovereignty and non-intervention further restricts the activities of mercenaries, as their involvement in conflicts can undermine the territorial integrity and political independence of states.

Case Law

There have been relatively few high-profile cases involving British mercenaries. One notable case is that of Simon Mann, a former British Army officer involved in an attempted coup in Equatorial Guinea in 2004. Mann was convicted in Zimbabwe and Equatorial Guinea for his role in the coup plot, highlighting the potential legal consequences for British citizens engaging in mercenary activities abroad.

Regulation and Oversight

Governmental Oversight

In the UK, several government bodies are involved in the oversight of mercenary activities. The Ministry of Defence (MoD) and the Foreign, Commonwealth and Development Office (FCDO) play key roles in monitoring and regulating the involvement of British citizens in foreign conflicts. These departments can issue advisories and restrictions on travel to conflict zones and guide on the legal implications of engaging in mercenary activities.

Parliamentary Scrutiny

Parliamentary committees, such as the Defence Select Committee and the Foreign Affairs Committee, also provide oversight by scrutinising government policies and actions related to private military contractors and mercenaries. These committees can conduct inquiries, gather evidence, and make recommendations to the government to ensure compliance with domestic and international legal standards.

Ethical and Human Rights Considerations

The use of mercenaries raises significant ethical and human rights concerns. Mercenaries are often perceived as operating outside the bounds of legal and moral accountability, potentially committing human rights abuses with impunity. The lack of regulation and oversight can lead to violations of international humanitarian law, including the targeting of civilians, torture, and extrajudicial killings.

The Role of Private Military Companies (PMCs)

Private Military Companies (PMCs) are often conflated with mercenaries, though they operate under a different legal framework. PMCs provide a range of services, including security, logistics, and training, and are usually contracted by states, international organizations, or corporations. In the UK, PMCs are subject to the Private Security Industry Act 2001 and must obtain licenses from the SIA. However, the regulation of PMCs operating abroad remains limited, raising concerns about accountability and oversight.

International Cooperation

Effective regulation of mercenaries requires international cooperation. The UK collaborates with other countries and international organizations to address the challenges posed by mercenaries and private military contractors. This cooperation includes sharing intelligence, coordinating law enforcement efforts, and participating in international forums to develop common standards and best practices.

Challenges and Future Directions

The regulation of mercenaries in British law faces several challenges. These include the difficulty of enforcing laws against individuals operating in foreign jurisdictions, the evolving nature of conflicts and the roles of private military contractors, and the need for comprehensive international frameworks. Future efforts to address these challenges may involve updating domestic legislation, enhancing international cooperation, and strengthening mechanisms for accountability and oversight.


The legal framework governing mercenaries in the United Kingdom is complex, involving a combination of domestic laws, international treaties, and customary international law. While the Foreign Enlistment Act of 1870 provides a basis for regulating the involvement of British citizens in foreign conflicts, there are significant gaps in the regulation of modern private military contractors and mercenaries. Addressing these gaps requires a multifaceted approach, including updating legislation, enhancing oversight mechanisms, and fostering international cooperation. By doing so, the UK can better ensure that mercenaries and private military contractors operate within the bounds of law and respect human rights and international humanitarian principles.

Mercenary FAQ'S

Hiring a mercenary is generally illegal in most countries. The use of mercenaries is often considered a violation of international law and can lead to severe legal consequences.

Yes, mercenaries can be held accountable for their actions. They can be subject to criminal charges and prosecution for any illegal activities they engage in, such as human rights abuses or war crimes.

Yes, there are international legal regulations for mercenary activities. The International Convention against the Recruitment, Use, Financing, and Training of Mercenaries, adopted by the United Nations in 1989, prohibits the use of mercenaries and establishes legal obligations for states to prevent and punish their activities.

No, mercenaries are not considered legitimate combatants under international law. They do not enjoy the same legal protections as regular soldiers and can be treated as unlawful combatants if captured.

Yes, if a mercenary commits a crime in one country and is apprehended in another, they can be extradited to the country where the crime was committed to face legal proceedings.

In some rare cases, certain countries may have specific legal provisions allowing the use of private military contractors or security firms. However, these provisions are highly regulated and subject to strict oversight.

Mercenaries cannot claim self-defence as a legal defence for their actions. Their involvement in armed conflicts is often considered unlawful, and they can be held responsible for any violence they perpetrate.

Yes, if a mercenary causes harm or damages property, they can be sued for compensation. Civil lawsuits can be filed against mercenaries to seek financial restitution for their actions.

Amnesty for mercenaries is highly unlikely. Given the serious nature of their activities, it is rare for governments or international bodies to grant amnesty to individuals involved in mercenary actions.

Yes, even if a mercenary is working for a legitimate government, they can still be prosecuted if their actions violate international law or commit crimes. The affiliation with a government does not exempt them from legal consequences.

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This site contains general legal information but does not constitute professional legal advice for your particular situation. Persuing this glossary does not create an attorney-client or legal adviser relationship. If you have specific questions, please consult a qualified attorney licensed in your jurisdiction.

This glossary post was last updated: 8th June 2024.

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