Originally Posted by AllieKat

AFAIK, it wouldn't be illegal unless you were trying to deceive, which... given those don't look remotely like a French passport. They're the wrong colour for an EU passport, the typeface of "passport" is wrong, and the coat of arms... well, what even is that in the middle?

The item is clearly not a French passport, and doesn't even have the right colour to be seen as an EU passport at a glance. You normally present your passport open, as well. Since it's so obviously a wallet, not an attempt at fraud, I can't imagine anyone in their right mind trying to cause trouble over it.

Personally, I still suggest taking it out - it's much easier for them to handle your passport with no covers.