As airsoft has become popular, many new businesses have sprung up, and with them new regulations. Each country will have its own regulations, so it's important to know what they are before buying a replica. In France, replicas are considered dummy weapons. Sale or even gift is forbidden to minors under 18 when the replica is over 0.08j and under or equal to 2j. Wearing the uniforms or ranks of units or administrations such as the army, gendarmerie, national police or municipal police is totally forbidden. As for transporting and wearing replicas, there's no real legislation on this, but it's always best to avoid doing so in public places. Alsace and Moselle have different regulations, so be sure to get the facts.
Here's a summary table from the L'airsofteur website, which gives a good overview of replicas and their associated powers and distances.