The Precautionary Principle states that in the absence of scientific certainty, risk managers should err on the side of safety. The Precautionary Principle is routinely practiced by federal agencies when they are not otherwise statutorily constrained, such as by a requirement to balance benefits and costs. Indeed, it is rare when Congress has delegated the choice of risk management framework to an Executive branch agency and that agency has chosen any framework other thanks some variant of the Precautionary Principle.
A rare event is happening before our eyes. In the case of Ebola Virus Disease, federal risk managers are not relying on the Precautionary Principle. Rarer still, they are criticizing governors for relying on it.