Character A is wearing a Browing Hi-Power in a shoulder holster while his unarmed (and unwilling) partner follows him around Paris at three in the morning. It's dark, it's late, they're nearing the Palais du Luxembourg; I imagine there would be more security in the area, and I was planning for them to be stopped and politely searched, and then the Browning is found...
What kind of trouble would they get into, especially if Character A puts up a fight, and Character B jumps out of the way and lays low?
Google searching turned up a mediocre article that contained the background information I needed on gun ownership in France in general: http://findarticles.com/p/articles/mi_m0BTT/is_159_26/ai_90099728/ As I understand it, one must be part of a gun club for six months and have the confidence of the club president to submit the proper paperwork needed to have guns at home for self-defense.
But otherwise, "concealed carry laws in France" didn't turn up anything for me, and I wouldn't be stupid enough to try this kind of thing... :D (It also seems to me that after doing a google map search that Luxembourg Palace isn't really close to Paris proper, though it is stated to be located in the sixth arrondissement; I'm not sure how this would affect the situation.)