Related Rule
Practice Relating to Rule 108. Mercenaries
Section A. Definition of mercenaries
In 2005, in a report in response to a parliamentary postulate on private security and military companies, Switzerland’s Federal Council stated:
5.1 Rules of international law concerning mercenarism
5.1.1 Art. 47 of the First Additional Protocol of 1977
International humanitarian law contains only one provision specifically concerning mercenary activity, namely Article 47 of the first additional protocol of 1977 (AP1). Additional Protocol I has been ratified by a large majority of states.
As understood by the first paragraph of this provision, Article 47 AP1 does not forbid mercenary service, although especially African countries had wished otherwise during negotiations on this provision. However on the basis of Article 47 AP1, mercenaries can be denied the privileged status of a combatant or prisoner of war. In particular, mercenaries, in contrast to combatants and prisoners of war, can be held criminally responsible by the opposing state merely for having taken part in an international armed conflict.
However a state is not obliged to deny prisoner of war status; the mercenary simply has “no claim” to such status. Even if prisoner of war status is denied, mercenaries are not totally unprotected. Under Article 75 AP1 they enjoy a minimum protection which has the character of customary international law.
The significance of Article 47 AP1 is infinitesimal in practice. In paragraph 2, the list of six cumulative definitions is so restrictive that it becomes difficult to prove that employees of a private security company fall under the description. The majority of private military companies indeed offer inherent military services, but are only seldom directly involved in hostilities. Finally, by definition, citizens of a country in conflict cannot be considered mercenaries. Actually, one must proceed from the fact that only a small part of employees of private security companies involved in military functions and active in conflict situations could be qualified as mercenaries.
5.1.2 Relevant instruments of the UN and individual regional organisations
In 1970, the UN General Assembly adopted the Friendly Relations Declaration 2625 (XXV) concerning principles of international law relating to friendly relations and cooperation between states. …
One of the specifications [in this Declaration] states:
“Every State has the duty to refrain from organising or encouraging the organisation of irregular forces or armed bands including mercenaries, for incursion into the territory of another State.”
This declaration of 1970 therefore makes it a duty of the state not to use mercenaries against the territorial integrity or independence of another state. The explicit reference to mercenary service by the UN General Assembly represents something new in the way the issue of mercenary service is dealt with internationally because international law had never before come to grips with this topic. However, the declaration does not define what is meant by “irregular forces or armed bands”.
On 3 July 1977 the African Union, AU, (formerly Organisation of African Unity, OAU) accepted the Convention for the Elimination of Mercenarism in Africa. Article 1, par. 1 of this convention defines the term mercenary almost word-for-word the same as in Article 47 AP1. As already mentioned, this makes it difficult in practice to legally qualify someone as a mercenary on the basis of the AU convention. The convention however does not bar the States Parties from using mercenaries in operations against dissident groups within their own borders.
The UN Convention against the Recruitment, Use, Financing and Training of Mercenaries of 4 December 1989 defines the term mercenary in Article 1, par. 1 in a way closely resembling that in Article 47 AP1. Here too, it is difficult in practice to qualify who is a “mercenary” due to the definition in the UN Convention. Nevertheless the definition in the UN Convention goes slightly beyond the one in Additional Protocol I in that it takes into consideration not only situations of armed conflict but also of organised violence to bring about the collapse of a government, to undermine constitutionality or against the territorial integrity of a state.
The United Nations Convention criminalises the recruitment, financing, training and the use of mercenaries as well as the active participation of mercenaries even in the organised use of force. These activities are to be forbidden by the States Parties.
The UN Convention entered into force more than 10 years after its adoption. Switzerland has so far not ratified the convention. The issue of ratification was not a priority in the 1990s, particularly because there were different opinions regarding its effectiveness. The UN Convention does not reflect customary international law as can be seen by the small number of ratifying countries.
5.1.3 Conclusions: Customary international law does not prohibit mercenarism
While Article 47 AP1 and the Friendly Relations Declaration of the UN do not forbid mercenarism, the AU Convention of 1977 and UN Convention of 1989 are by no means universally accepted legal instruments. Therefore customary international law does not forbid mercenarism and contains no specific standards limited only to mercenary activities.
With reference to the Conventions of the AU and the UN, it must be noted that several of the defining elements set down are so restrictive and difficult to prove that the practical relevance of the Conventions even for States Parties is limited. Both Conventions deal mainly with individuals acting against national governments and are not intended to regulate the operations of private security companies in general conflict situations. The concept of the “mercenary” is for these reasons partly described as outmoded and considered inappropriate for the practical regulation of the phenomenon of private military and security companies. 
Switzerland, Report by the Swiss Federal Council on Private Security and Military and Companies, 2 December 2005, pp. 42–44.
[emphasis in original; footnotes in original omitted]
Switzerland’s ABC of International Humanitarian Law (2009) states:
Mercenaries participate in Armed conflicts without belonging to the armed forces and without sharing the nationality of any of the parties to the conflict. Nor are they residents of areas occupied by any of the parties to the conflict. Mercenaries operate purely for their own material benefit. The First Additional Protocol to the Geneva Conventions (1977) denies mercenaries both the status of Combatants and of Prisoners of war. 
Switzerland, Federal Department of Foreign Affairs, ABC of International Humanitarian Law, 2009, p. 35.