For the Federal Goverment: https://en.wikipedia.org/wiki/Public_Health_Service_Act
The list (for the federal government) of diseases is managed via Executive Order [PDF] https://www.govinfo.gov/content/pkg/FR-2003-04-09/pdf/03-883...
The CDC also has a link to this: https://www.cdc.gov/quarantine/aboutlawsregulationsquarantin...
These measures have precedent, so good luck in getting these overturned.