The Federal Government is granted these powers through federal statute, the Commerce Clause within the Constitution, and executive order of POTUS.

Also:

> In addition to serving as medical functions, isolation and quarantine also are “police power” functions, derived from the right of the state to take action affecting individuals for the benefit of society.

https://www.cdc.gov/quarantine/specificlawsregulations.html

https://www.cdc.gov/quarantine/aboutlawsregulationsquarantin...