The international definition of Crime against humanity is set forth in the Charter of the International Military Tribunal, which was agreed to following World War II in preparation for the Nurnberg Trials . This definition was confirmed by resolutions of the General Assembly of the United Nations in 1946.

It is defined as murder, extermination, enslavement, deportation, and other inhumane acts committed against any civilian population; or persecution on political, racial or religious grounds in execution of or in connection with any crime, whether or not in violation of domestic law of the country where perpetrated.

It should also be noted that leaders, organizers, instigators and accomplices participating in the formulation or execution of a common plan or conspiracy to commit any of the foregoing crimes are responsible for all acts performed by any persons in execution of such plan.

http://www.ess.uwe.ac.uk/documents/chtrimt.htm