PDR1 - the law on breathalysers was never put into effect by the French. Technically still on the books but never enforced. I don't even think you can buy them anymore. I had some but they were years beyond the 'use-by' date before I binned them.
If you are coming to Switzerland and take the car into EU for a day I don't think this rule applies. For example if your in the West and want to drive to Ticino, the quickest route is through Italy.