Those who emphasize individual or local choice, may view fluoridation as a violation of ethical or legal rules that prohibit medical treatment without medical supervision or informed consent, and that prohibit administration of unlicensed medical substances,[1][63] view it as "mass medication",[64] or may even characterize it as a violation of the Nuremberg Code and the Council of Europe's Biomedical Convention of 1999.[9][65][66] Another journal article suggested applying the precautionary principle to this controversy, which calls for public policy to reflect a conservative approach to minimize risk in the setting where harm is possible (but not necessarily confirmed) and where the science is not settled.[67] Others have opposed it on the grounds of potential financial conflicts of interest driven by the chemical industry.[68]