In December 1968 Israeli forces launched an attack on Beirut Airport, claiming as justification, inter alia, Lebanese responsibility under international law for a number of incidents involving damage to life and property caused, it was alleged, by groups operating from the Lebanon 1). The action, which was the culmination of a long series of attacks by Arab groups, and similar earlier reactions, received widespread criticism, and have had far-reaching political consequences, but in contrast there has been little legal analysis of the underlying problems raised by the existence and activities of private groups operating from one country with violent acts against another country or of the remedies available to the State attacked. The political immediacy of these incidents has even led writers to employ circumlocutions or arbitrary cumulations of terms in order, it seems, to avoid committing themselves. In an article discussing the Beirut raid 2) Falk suggests that the language used to characterize acts of violence by non-State groups is either cumbersome or implies a degree of sympathy with, or antipathy to, such activities. He therefore uses such terms as “terrorist”, “guerrilla activity”, “liberation movement” and “freedom fighters” interchangeably. In a reply 3), Blum claims that “guerrilla” is “devoid of implying political values” and uses the word throughout 4).