Laifin yaki wani aiki ne wanda ke haifar da mummunan keta dokokin yaƙi wanda ke haifar da ɗawainiyar aikata laifi. Misalai da laifukan sun hada da gangan ya kashe fararen hula ko fursunonin, da azabtarwa, da hallaka farar hula dukiyõyin su, da aka yi garkuwa, yin wani perfidy, raping, yin amfani da yara, pillaging, yana nuna cewa babu kwata za a ba, da kuma tsanani keta ka'idojin bambanci, proportionality, da kuma wajibcin soja . Batun aikata laifukan yaƙi ya samo asali ne a ƙarshen karni na ashirin lokacin da aka tsara kundin dokokin ƙasa da ƙasa da suka shafi yaƙi tsakanin ƙasashe masu mulkin kansu . Irin wannan bayanin ya faru ne a matakin kasa, kamar buga littafin Lieber Code a Amurka, da kuma a matakin kasa da kasa tare da amincewa da yarjejeniyoyi a lokacin yayin taron Hague na shekarun 1899 da 1907. Bugu da ƙari, shari'o'in da aka yi a kotunan ƙasa a wannan lokacin sun ƙara bayyana doka. Bayan ƙarshen Yaƙin Duniya na II, manyan cigaba a cikin dokar sun faru.