The French may not be as litigious as Americans (who in my opinion have gone somewhere off the deep end in their penchant to sue) but that doesn't mean that there aren't rules for what to do when and who exactly is responsible for any mayhem that may result when those rules are not respected. If you look closely, you will find a sign like this one in every park and garden owned by the city of Paris. Most of the time, it's right there by the entrance.
If you read the fine print, most of the rules are pretty much common sense: no fires or barbecues, don't pick the flowers or climb the trees, and restrict activities to the areas designated for their use. But there are also a few that made me sit up and take notice. For example, you can fly kites in fields as long as they go no higher than 50 meters, and sales of animals are forbidden. Fine by me. If you feel the need to practice your French or if you've got some crazy scheme in mind and just want to be sure that you're on the right side of the law, you can check it out here.