It is true that here the target of the contemplated operations would be a U.S. citizen. But
we do not believe ²³V„9ÞÙg’s citizenship provides a basis for concluding that section 1119 would fail to incorporate the established public authority justification for a killing in this case. As we have explained, section I 119 incorporates the federal murder a11d manslaughter statutes, and thus its prohibition extends only to “unlawful” killings, 18 U.S.C. §§ 1111, 1112, a category that was intended to include, from all of the evidence of legislative intent we can find, only those killings that may not be permissible in light of traditional justifications for such action.
At the time the predecessor versions of sections 1111 and 1112 were enacted, it was understood that killings undertaken in accord with the public authority jlL<>tification were not “unlawful” because they were justified. There is no indication that, because section 1119(b) proscribes the unlawful killing abroad of U.S. nationals by U.S. nationals, it silently incorporated all justifications for killings except that public authority justification.