[CRNpolyfluoric]

This is all a little too vague.  The term "murder" itself implies an innately unjustifiable killing, while the term "justifiable homicide" fits your concept better.  
Before the media appropriated the term "honor killing" to describe the unjustifiable slaying of women in Islamic nations that would have worked well, but now perhaps we have to use "vig" (see below).

murder (n.) Look up murder at Dictionary.com
c. 1300, murdre, from Old English morðor (plural morþras) "secret killing of a person, unlawful killing," also "mortal sin, crime; punishment, torment, misery," from Proto-Germanic *murthra- (source also of Goth maurþr, and, from a variant form of the same root, Old Saxon morth, Old Frisian morth, Old Norse morð, Middle Dutch moort, Dutch moord, German Mord "murder"), from PIE *mrtro-, from root *mer- "to die" (see mortal (adj.)). The spelling with -d- probably reflects influence of Anglo-French murdre, from Old French mordre, from Medieval Latin murdrum, from the Germanic root.
   Viking custom, typical of Germanic, distinguished morð (Old Norse) "secret slaughter," from vig (Old Norse) "slaying." The former involved concealment, or slaying a man by night or when asleep, and was a heinous crime. The latter was not a disgrace, if the killer acknowledged his deed, but he was subject to vengeance or demand for compensation.
  Mordre wol out that se we day by day. [Chaucer, "Nun's Priest's Tale," c. 1386]


Poly