Entry Restrictions at the Northern and Southern Borders in Response to COVID-19 [Updated April 27, 2020] [open pdf - 638KB]
From the Document: "In response to the global spread of COVID-19 [coronavirus disease 2019], the federal government has issued several orders restricting the entry of foreign nationals into the United States. Many of these restrictions were implemented through President Trump's authority under Section 212(f) of the Immigration and Nationality Act (INA) to suspend the entry of non-U.S. nationals (aliens) whose entry the President 'finds ... would be detrimental to the interests of the United States.' [...] The Trump Administration has taken other action, relying on authority outside INA Section 212(f), to restrict the movement of foreign nationals over land borders into the United States. Two orders restrict non-essential travel by foreign nationals into the United States through ports of entry on the land borders with both Canada and Mexico. Additionally, the Centers for Disease Control and Prevention (CDC), a component of the Department of Health and Human Services (HHS), has issued an order (along with implementing regulations) suspending the 'introduction' of foreign nationals from countries with COVID-19. These new orders raise a number of legal issues--most notably their effect on migrants seeking asylum in the United States."
CRS Legal Sidebar, LSB10439
Congressional Research Service: https://crsreports.congress.gov/