I was wondering how you'd word such a rule. Is the symbol forbidden, or wearing it with some intent? What's if it's dual use, a piece of clothes but also associated with a religion? Can I wear a Kufiya that can be viewed as a political statement? Is that okay? It also touches religion. What about a bit more subtle symbols, a fish instead of wearing a cross? It's kind of a slippery slope.
Or the heavy metal t-shirt i mentioned. These are most of the times not religious at all but use christian or northern mythology and those imagery. They also do not mock religion except you're a super insecure fundamentalist.
Do we only forbid religious imagery, or also that of cults? Is there a line? Can I wear my spaghetti monster shirt? Wear pirate insignia?
I'm genuinely interested in how the french people/legislator solve the issue with the whole thing being a slippery slope and kind of vague. I'm a fan of laicism myself.