Notwithstanding the faüures of United States counternarcotics policy, this article explains the reasons why different administrations continué to insist upon its preservation, making use of a legitimating discourse. According the author, the analysis of anti-drug policy requires a historical approach to the causal and constitutive elements ofthe campaign against illegal substances, and an overview of the ways in which this problem has been defined in public discourse. If policy is based upon a prohibitionist strategy or ifdrugs are identified as a security problem, a logic of appropriation prevails. On the other hand, ifpolicies are based upon instrumental strategies, a logic of expected consequences becomes operational. The article defines these two logics and evaluates themfrom the Nixon to Clinton administrations.