Legal framework

Definition and Treaty Law

Unlike other international crimes, such as genocide, crimes against humanity have not been codified in a comprehensive international treaty. International tribunals (both ad hoc and permanent) charged with prosecuting crimes against humanity typically employ somewhat different definitions of this crime.

The Rome Statute offers a definition that reflects the latest consensus of the international community and may currently be considered the most authoritative definition of crimes against humanity:

Article 7. Crimes Against Humanity

For the purpose of this Statute, "crime against humanity" means any of the following acts when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack:

(a) Murder;
(b) Extermination;
(c) Enslavement;
(d) Deportation or forcible transfer of population;
(e) Imprisonment or other severe deprivation of physical liberty in violation of fundamental rules of international law;
(f) Torture;
(g) Rape, sexual slavery, enforced prostitution, forced pregnancy, enforced sterilisation, or any other form of sexual violence of comparable gravity;
(h) Persecution against any identifiable group or collectivity on political, racial, national, ethnic, cultural, religious, gender as defined in paragraph 3, or other grounds that are universally recognised as impermissible under international law, in connection with any act referred to in this paragraph or any crime within the jurisdiction of the Court;
(i) Enforced disappearance of persons;
(j) The crime of apartheid;
(k) Other inhumane acts of a similar character intentionally causing great suffering, or serious injury to body or to mental or physical health.

This definition is also employed by the Ljubljana-The Hague Convention.

Development of a Specialised Convention

Efforts to develop a dedicated treaty on crimes against humanity have been underway since the early 2000s. The International Law Commission adopted Draft Articles on Prevention and Punishment of Crimes Against Humanity in 2019, recommending that the UN General Assembly or an international conference of plenipotentiaries elaborate a convention.

In 2024, the Sixth Committee adopted a resolution advancing the draft articles to formal negotiations. Preparatory sessions are scheduled for 2026 and 2027, with the treaty expected to be finalised during three-week negotiations in 2028 and 2029.

Customary Law Status and the European Court of Human Rights

The maxim nullum crimen sine lege (no crime without law) — a fundamental principle of international criminal law — dictates that individuals can only be convicted for specific acts that were known to be criminal at the time of commission.

Crimes against humanity are fundamentally inhumane acts that would constitute crimes under most national criminal law systems worldwide, committed as part of a widespread or systematic attack against civilians. Given this customary law foundation, the European Court of Human Rights has repeatedly found that retrospective application of crimes against humanity legislation to acts committed before such crimes were incorporated into domestic penal codes does not violate the principle of legality enshrined in Article 7 of the European Convention on Human Rights.

Read further