Currently Title 10 Armed Forces are prohibited from engaging in civilian law enforcement. While the Navy/Marine Corps aren’t mentioned in Posse Comitatus, they are statutorily prohibited to the same extent.
So the ‘piece to go’ is making that possible. Or allowing an expansion that allows them to assist the Marshals/Secret Service or some untitled law enforcement entity to a greater extent than is now possible under the law.
**********
How much, if any, of that changes when the entire country is in a State of Emergency?
All 50 states by independent declaration of each of their governors?
As regards the military use in law enforcement, I don't think it changes anything. But, I'm not a JAG and hate lawyers especially when I don't need one.
Congress can authorize such an action, but won't here. With enough unrest, the President can declare martial law. That would suck but it would suck more for the DS perps. Tough to envision in an election year.
This from Wiki is kinda interesting:
The 1977 International Emergency Economic Powers Act allows the government to freeze assets, limit trade and confiscate property in response to an "unusual and extraordinary threat" to the United States that originates substantially outside of it. As of 2015 more than twenty emergencies under the IEEPA remain active regarding various subjects, the oldest of which was declared in 1979 with regard to the government of Iran. Another ongoing national emergency, declared after the September 11 attacks, authorizes the president to retain or reactivate military personnel beyond their normal term of service.[113]
'substantially outside', could mean 'look out coup plotters' after the Covid. You could make the case the transnational 'families' are substantially outside the US so they and their 'local' cohorts could be at risk.