Abstract
OBJECTIVE To discuss the negative and positive concepts of liberty and postulate its interdependent and complementary relationship in the evaluation of public policy intersectoral actions, taking water fluoridation as a case. METHOD To describe scopes and limits regarding 1950s Isaiah Berlin's distinction, showing its validity in facing the harmful effects of an uncontrolled market economy and an autocratic political regime. RESULTS Both the rights that protect citizens against a powerful state and the rights that protect the state against powerful citizens were equally acknowledged as crucial. CONCLUSION We argued that, in a context in which negative and positive liberties are balanced, regulatory policies have double meaning. Thus, there should be a balance between the establishment of necessary rules for social protection and limits for them not to violate individuals' rights.