re: Traveling back into the US from overseas

Maybe not. However, the CDC is requiring the airlines to check this “abroad” and have instructed them to deny boarding of a US citizen with no test. In essence, denying entry into the US.

There is a reason they are doing this through the CDC, and not Homeland Security once you arrive.

It doesn’t pass the sniff test, and should be challenged in court. Just because it is an EO, or “policy” doesn’t make it Constitutional.