The controversy over packing therapy used in psychiatry was studied here to illustrate how leading associations can influence public health policies. The main French associations of parents with autistic children succeeded in obtaining the prohibition of packing, announced by the French Secretary of State to the Ministry of Health in April 2016. Parents and professionals who had observed the positive effects of packing when nothing else worked for their part wondered what could be done for self-harming patients. The political authorities followed the opinion of the main associations of parents with autistic children at the expense of that of professionals. In this paper, the actions and discourse of the associations against packing are explored, as are the arguments of the psychiatrists who defend packing therapy. The different phases in the controversy from the first opposition in 2005 and the role of opinion leaders in associations are analyzed. The strategies to discredit psychiatry and to promote behavioral methods are also studied to understand the shift in the balance of power from professionals to association leaders. The mobilization of the associations prompted some psychiatrists to conduct evidence-based research and to formalize their practice. The controversy over packing, involving political decision-making processes, ethical issues and clinical questions, enables us to illustrate a new form of lobbying.