Adding another voice to the chorus - please, if you are crossing borders with cats (or dogs or ferrets), please follow the travel regs. The online tool to show what you need is here: http://blv.bytix.com/plus/dbr/default.aspx?lang=de
Yes, I know - much of the time Swiss officials pay little attention to their own rules. I've crossed manned borders during office hours many times where the official could not be bothered to check our documentation, despite a car full of very visible and audible mutts.
The problem I often see is that people become complacent with lack of enforcement. But just as laws and regs are capriciously ignored by Swiss officials, I've also seen the same laws and regs equally capriciously enforced.
This is a risk no pet owner should take - because it is your pet who could pay the price.
When you get your cats chipped, do register the chip in ANIS, the Swiss database for cats, and in whatever French database(s) your vet there recommends. Registration in a locally (or nationally) used database is what helps your lost pet find it's way back to you.
I don't know what databases are available in France... as my French foundling was tattoo'd (before the widespread use of chips) but not registered. Which is how he ended up on death row. (Thank doG for the shelter worker who went above and beyond!)