Legal tools for preparedness and response: variation in quarantine powers among the 10 most populous US states in 2004.

From April 2004 through December 2004, we reviewed the express legal authorities of the 10 most populous US states to restrict the movement of persons to control communicable diseases. All 10 of the states possessed express legal authority to quarantine and isolate individuals, but the laws varied substantially. In the absence of declared emergencies, only 4 states had express authority to conduct area quarantine, and only 2 states had express authority to conduct group quarantine. During declared emergencies, 7 states had additional authorities for area quarantine. Express authorities are only part of states' legal powers to employ such movement restrictions, but substantial variation in express authorities across states could present potential challenges for the coordination of large national or regional epidemics.