ICRC Customary IHL, Chapter 44. War Crimes.

Same drill as before: link, blackletter rule, commentary; except the first commentary is much longer (28pp.). They all have to be read to understand the rules' applications.

156. Definition of War Crimes

Rule 156. Serious violations of international humanitarian law constitute war crimes.

157. Jurisdiction over War Crimes

Rule 157. States have the right to vest universal jurisdiction in their national courts over war crimes.

158. Prosecution of War Crimes

Rule 158. States must investigate war crimes allegedly committed by their nationals or armed forces, or on their territory, and, if appropriate, prosecute the suspects. They must also investigate other war crimes over which they have jurisdiction and, if appropriate, prosecute the suspects.

159. Amnesty

Rule 159. At the end of hostilities, the authorities in power must endeavour to grant the broadest possible amnesty to persons who have participated in a non-international armed conflict, or those deprived of their liberty for reasons related to the armed conflict, with the exception of persons suspected of, accused of or sentenced for war crimes.

160. Statutes of Limitation

Rule 160. Statutes of limitation may not apply to war crimes.

161. International Cooperation in Criminal Proceedings

Rule 161. States must make every effort to cooperate, to the extent possible, with each other in order to facilitate the investigation of war crimes and the prosecution of the suspects.
So much for black-letter rules.

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What follows is a more important issue to me, which I have mulled over the last two years; and which I will address candidly.

James Spaight contended in 1911 that:

[T]he International Law of War ... is a quasi-military subject in which no one, in the army or out of it, is very deeply interested, which everyone very contentedly takes on trust, and which may be written about without one person in ten thousand being able to tell whether the writing is adequate or not.
My conclusion is that nothing has changed in a century; the international laws of war are a minimal topic with little value added for most people; and that topic is probably better left to specialized sites such as Lawfare and Opinio Juris, where there is peer review. If I'm wrong, please tell me why.

Regards

Mike