No. The will reflects the last wishes of its author. Therefore, if you appoint an association as the universal legatee, it has the option to accept or decline the bequest (Article 724-1 of the Civil Code). If it declines and you have not designated a secondary legatee, the rules of legal succession will apply (in the absence of a surviving spouse and children, your legal heirs are your parents and siblings, or their descendants if they have also passed away).