Here's an ET doll being sold on a French web site:
E.T. L´EXTRA-TERRESTRE RÉPLIQUE POUPÉE E.T. STUNT PUPPET 91 CM

Maybe that doesn't cont as a "human" body, but whatever. I Googled for for poupee+stroumph and found them being sold on ebay.fr

IMO this shows that if there is such a law, it's not enforced.
There's this comment on a straightdope user forum:
Good suggestion, A Monkey With a Gun. It prompted me to do some
googling. The first thing I found was actually a Canadian proposal
(http://www.parl.gc.ca/36/1/parlbus/chambus/house/bills/private/C-374/C-374_1/361282bF.html)
for a law making it an offense to sell a doll (poupée) with the
encouragment to have it suffer degrading treatment. The explanation
(http://www.parl.gc.ca/36/1/parlbus/chambus/house/debates/220_1999-05-03/han220_1105-f.htm)
mentions:
Pourquoi a-t-on mis le mot «poupée» dans ce projet de loi? C'est parce
que les mots ont un sens dans notre langue. En français, le mot
«poupée» veut dire tout objet ayant une forme humaine.
Why is the word 'doll' used in this proposal? It is because words have
a meaning in our language. In french, the word 'doll' (poupée) means
an object having a human form.
This seems to confirm your suspicion.
Then I checked Legifrance
(http://www.legifrance.gouv.fr/html/index.html), which should contain
all French laws. The search function only got me one law, the 'Arrêté
06 juillet 1995', listing movie titles, one of which was 'Maison de
poupée' (Doll house).
Based on this, I do call bullshit, with the proviso that there may be
a different regulationt that isn't law and/or isn't listed on
Legifrance, or that the OP's source meant a different word (which
would however be unlikely given the earlier Canadian quote).
I guess this is the best we can do at the moment, since it is hard to
prove something doesn't exist. Maybe clairobscur, if he drops by, can
enlighten us.
It suggests that perhaps there's a law which defines a doll as being "something with a human face".
The 3rd May 1999 edition of Hansard is where that legal definition was discussed in Canadian Parliament in French (in the context of a rejected law making it illegal to sell dolls towards which the buyers are encouraged to be cruel).
I confirm that my search for "poupée" on http://www.legifrance.gouv.fr/initRechTexte.do using "Rechercher ces mots parmi les mots du texte (depuis 1990)" returns nothing -- or more precisely it returns 31 hits, none of which are related to the alleged law in question.
This one does say "Poupées représentant uniquement l'être humain" but what it's doing is saying that (among many other things) "dolls which represent humans" have a reduced tariff, in a trade agreement between Serbia and the EEC
This one says that "poupées" and "peluches" (i.e. "dolls" and "plush toys") are two of the types of thing made by the industry of games and toys.