As Joe Gould once said:
In the Winter I’m a Buddhist,
And in Summer I’m a Nudist.
Since it was a summary procedure, there wasn’t much detail about the reasons of the decision, but it seems to be more based on constitutionally guaranteed freedoms and even simply the law. Basically, the State Council stated that the mayor had no legal right to restrict fundamental liberties without proving that it was strictly necessary to prevent serious risks against the public order
They pay a lot of attention to it. Like in the USA, there are decades-old, or century-old precedents that are still standing. And studying them is a large part of studying law.
The difference is that French courts aren’t obligated to follow a precedent. So, in theory, a lower court could find differently about the same issue. But it’s extremely unlikely to happen, especially since the State Council just decided about it, hence a contrary decision would be appealed and cancelled.
But it happens that a change in a long-standing precedent is initiated by a lower court, and then confirmed by higher courts. As far as I understand, that wouldn’t be possible in the USA, for instance.
On my last beach vacation, I was surrounded by all manner of skimpy bikinis as well as topless women. I found myself at one point watching the only two burkini clad women I’d ever seen. They were incredible colors, and for some reason they were a real turn on (apologies to allah).