I suppose France and Switzerland would have the authority to stop the project as a mere expression of sovereignity.

Assuming arguendo that the project is legitimately dangerous? (I really don't know). Its clear that actions in one country can have negative externalities in another. We can look at riparian rights (international rivers) over the course of years, we can look at events like Chernobyl, global warming, etc. I think its clear that a nation state must consider the costs and risks imposed on others beyond the borders of the traditional nation state.

I don't know! We will have to look at it on a case by case basis.

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