Within the authority of the President under 50 USC Chapter 34 and he will then send notice of changes in laws and regulations to Congress as needed.
Presidential Proclamation 9994 National Emergency due to Covid-19
https://www.federalregister.gov/documents/2020/03/18/2020-05794/declaring-a-national-emergency-concerning-the-novel-coronavirus-disease-covid-19-outbreak
50 USC Chapter 34 National Emergencies
§1621. Declaration of national emergency by President
§1631. Declaration of national emergency by Executive order )authority for changes in regulstions)
https://uscode.house.gov/view.xhtml?path=/prelim@title50/chapter34&edition=prelim
Should be noted that Congress has not yet made changes in 50 USC Chapter 34 to include the Amendment of Proclomation 9994. As it was placed in the Federal Register and Congress did receive a copy March 13, 2020 as noted in the Congressional Record, the statute should be amended accordingly.
Congress failed to perform their duty on the matter.