Punishment of grave breaches of Conventions and Protocol I
2. (4) Any person who is found guilty of an offence under this section is, subject to subsection (5), liable -
(a) in the case where the offence involves the willful killing of a person protected by the relevant Convention or by Protocol I, to imprisonment for life;
(b) in any other case, to imprisonment for a period not exceeding 14 years .
National penalties - war crimes
National penalties - national proceedings
EDIT.