I think a lot of regulations like that are administered at a local level.
The "mountain law" goes back as far as Decree 61-650 of 23 June 1961 to determine the geographic limits.
It's France after all - look at the circular history of "helipads" in St Tropez over the years. Unless you are French it will take you a lifetime to understand it.
For practice watch a few episodes of "Marseille" on Netflix and treat it as a training course!