Answer: actually it is forbidden not only to tell lies in publicity, but even to pretend to something you can’t warrant for, athough legislations are more or less tolerant on the subject. (French are quite severe, but luckily they usually have laws as museum pieces for visit, so that actually quite a lot of ambiguous publicity is available a little bit everywhere.) The last fashion in publicity ‘lies’ is in fact the constant misuse of concepts. Say for example: this is an antispamodic. An antispamodic acts on muscles and the gicen chemistry acts on the nervous system in order to act on muscles, secondarily. Factually it is not an antispasmodic. But who will ever know? From a legal point of view, there is attempt of misleading concerning the nature of a chemistry and this may have consequences.
Now, instead of telling lies you may just be cute. What about: Mustard is English. And some brand name behind. It’s a fact that the product is originally from France. Ah. But yes, they say moutarde and mustard is still English. See. That’s not forbidden.