Key here is the fact that the certification mark is a "collective" mark. It is owned not by you, the party using it, but by the body authorising you to use it (in this case AFNOR), provided that you and your products satisfy the required conditions. Thus, in the same way that you may not transfer the mark to other persons or entities who are not officially authorised by AFNOR and do not satisfy the required conditions, the mark or the right to use it is not an asset that may be subject to attachment or seizure or pledge for the purposes of enforcing a judgment or for the payment of a debt, as the party seeking the attachment or seizure would not be authorised to use the mark.
This is covered in Article L.715-2 of the French Intellectual Property Code
4° la marque collective de certification ne peut faire l'objet ni de cession, ni de gage, ni d'aucune mesure d'exécution forcée ;
http://www.celog.fr/cpi/lv7_tt1.htm#c54. a collective certification mark may not be subject to assignment, pledge or any measure of enforcement;
http://oami.europa.eu/genhtm/mark/nl_fr_1_en.htm
peer agreement (net): +2
