From the Document: "On December 31, 2020, President Trump issued a proclamation to extend Proclamation 10052, issued on June 22, 2020, through March 31, 2021. Proclamation 10052, among its other provisions, extends Proclamation 10014, issued April 22, 2020, which suspended the entry into the United States of certain aliens (foreign nationals) who are seeking lawful permanent resident (LPR) status (i.e., immigrants). The three proclamations justify the suspension to protect American workers from foreign labor market competition during a time of high domestic unemployment and reduced demand for workers caused by the coronavirus pandemic. The proclamations rely on two immigration-related legal authorities. Under the Immigration and Nationality Act (INA), §212(f) (8 U.S.C. §1182(f)), the President may suspend immigration when it would harm U.S. interests. Under INA §215(a) (8 U.S.C. §1185(a)) the President may prescribe limitations and exceptions on who may enter or depart the country."
CRS Insight, IN11362
Congressional Research Service: https://crsreports.congress.gov/