It is up to the insurer to prove the exclusion clause that it opposes to its insured. On the other hand, the guarantee conditions prove not the insured.
It is the responsibility of the insured person claiming insurance to provide proof of the existence of the insurance contract, the case law recalling in this respect that such proof must be provided in writing (Cass, 1st vic, 14 November 1995, appeal no 93-14.546, Bull. 1995, I, No. 402; Cass, 1st Civ., 2 March 2004, appeal No. 00-19. 871).