A program titled "Operation Valkyrie" was implemented by the Illinois State Police to interdict drugs. Information regarding this program was obtained from interviews with State police officials, from defense counsel who represented plaintiffs in interdiction cases, and from court records of Valkyrie interdictions. The authors suggest that two aspects of its institutional environment, the environment of legal precedent in which the program is embedded and the network of state and Federal agencies using similar interdiction strategies, influence the organization and activity of Operation Valkyrie. The article argues that current program activity reveals the way in which Operation Valkyrie is, in turn, affecting these two aspects of its institutional environment. Differences between Operation Valkyrie and traditional ideas of policing fall into three categories: (1) public consensus for the mobilization of the law; (2) a high degree of proactivity in law enforcement; and (3) the scope of the interdiction effort. Table, notes, references, cases cited