Related Rule
Luxembourg
Practice Relating to Rule 157. Jurisdiction over War Crimes
Luxembourg’s Code of Criminal Investigation (1944) provides:
Every foreigner who outside the territory of the Grand-Duché is responsible, whether as a principal or an accomplice, for the following:
(2) in wartime, abduction of minors; attacks on modesty or rape; prostitution or corruption of youth; murder or intentional bodily injury; attacks on individual liberty committed against a Luxembourg national or a national of an allied country,
can be prosecuted and tried according to the provisions of Luxembourg laws if he is found either in the Grand-Duché, an enemy country or if the government obtains his extradition. 
Luxembourg, Code of Criminal Investigation, 1944, Article 7.
Luxembourg’s Law on the Repression of War Crimes (1947) provides for the prosecution of non-Luxembourg nationals having committed war crimes
if such infringements have been committed at the occasion or under the pretext of war and if they are not justified by the laws and customs of war, these agents either being found within the Grand-Duché or on enemy territory, or the Government having obtained their extradition. 
Luxembourg, Law on the Repression of War Crimes, 1947, Article 1.
Luxembourg’s Law on the Punishment of Grave Breaches (1985) provides: “Any individual who has committed an offence under this law outside the territory of the Grand-Duché can be prosecuted in the Grand-Duché even though he may not be present there.” 
Luxembourg, Law on the Punishment of Grave Breaches, 1985, Article 10.