The little I know of this issue came from a webinar hosted by a large national law firm last week. The short of it was the Department of Homeland Security CISA memo was merely guidance that states could follow or not. The states generally retain authority over health and safety matters. A law passed by Congress on a specific health and safety issue could override the states but courts would narrowly construe it. The Department of Defense memo and the CISA memo last week both explicitly provide that they are guidance and not federal law.