a. Impediments to Performance
The primary basis for the promisor’s exemption is Art. 79 which deals with impediments outside of the seller’s sphere of responsibility. Art. 79(1) reads:
(1) A party is not liable for a failure to perform any of his obligations if he proves that the failure was due to an impediment beyond his control and that he could not reasonably be expected to have taken the impediment into account at the time of the conclusion of the contract or to have avoided or overcome it or its consequences.