From the Document: "The United States, along with many countries, is responding to an outbreak of a respiratory disease, now referred to as COVID-19 [coronavirus disease 2019], which is caused by a novel coronavirus first detected in mainland China's Hubei Province in late 2019. Cases of COVID-19 have now been detected in several countries, including the United States. To date, the federal government has taken two key actions to deter persons with suspected COVID-19 infection from entering the country or spreading the virus to persons within the United States. First, the federal government has restricted many non-U.S. nationals (aliens) who recently travelled to mainland China or Iran from entering the United States. Second, the federal government has imposed a quarantine requirement on all persons entering the United States, regardless of citizenship status, who have recently been to mainland China. This Legal Sidebar examines the legal authorities underlying these actions, as well as possible legal challenges to their use."
CRS Legal Sidebar, LSB10415
Congressional Research Service: https://crsreports.congress.gov/