The term brown bagging may not be familiar to all. It dates back to when not all restaurants had liquor licenses and you would take your own, discreetly of course, in a brown bag. This was a socially acceptable custom.
That said, would it be acceptable to carry a bottle of champage and flutes onto an evening cruise on the Seine? Or do they have bar service and prefer you buy from them? I'm referring to the regular, sight seeing cruise, not the dinner cruises.