A distinction must be made between the periods prior February 1979 and thereafter, when the Ayatollah Khomeini returned to Iran from exile. During the earlier period the thrust of the revolutionary movement was then aimed at the overthrow of the regime of Shah.
However, when the Ayatollah returned to Iran on February 1979 he was reported to have called for the departure of all foreigners. The implementation of this policy could, in general terms be violative of both procedural and substantive limitations on a state right to expel aliens from its territory, as found in the provisions of the Treaty of Amity and in CIL. However, it is necessary to examine the circumstances of each departure. The general turmoil is a factor to cause and individual’s decision to leave and which could not be attributed to the State or its agents or organs, claimant has not satisfied the burden of proving that the implementation of the new policy of the respondent was a substantial casual factor in his departure from Iran.