51 nevertheless remains that international law renders any State responsible for acts in breach of international law performed (i) by individuals having the formal status of organs of a State (and this occurs even when these organs act ultra vires or contra legem), or (ii) by individuals who make up organised groups subject to the State’s control. International law does so regardless of whether or not the State has issued specific instructions to those individuals. Clearly, the rationale behind this legal regulation is that otherwise, States might easily shelter behind, or use as a pretext, their internal legal system or the lack of any specific instructions in order to disclaim international responsibility. b. The Nicaragua Test is at Variance With Judicial and State Practice 124. There is a second ground – of a similarly general nature as the one just expounded - on which the Nicaragua test as such may be held to be unpersuasive. This ground is determinative of the issue. The “effective control” test propounded by the International Court of Justice as an exclusive and all-embracing test is at variance with international judicial and State practice: such practice has envisaged State responsibility in circumstances where a lower degree of control than that demanded by the Nicaragua test was exercised. In short, as shall be seen, this practice has upheld the Nicaragua test with regard to individuals or unorganised groups of individuals acting on behalf of States. By contrast, it has applied a different test with regard to military or paramilitary groups. 125. In cases dealing with members of military or paramilitary groups, courts have clearly departed from the notion of “effective control” set out by the International Court of Justice (i.e., control that extends to the issuance of specific instructions concerning the various activities of the individuals in question). Thus, for instance, in the Stephens case, the Mexico-United States General Claims Commission attributed to Mexico acts committed during a civil war by a member of the Mexican “irregular auxiliary” of the army, which among other things lacked both uniforms and insignia. 142 In this case the Commission did not enquire as to whether or not specific instructions had been issued concerning the killing of the United States national by that guard. 142 See United States v. Mexico (Stephens Case), Reports of International Arbitral Awards, vol. IV, pp. 266267. Case No.: -94-1-A 15 July 1999