You didn't offer any discussion, but the self-evident answer to the question is, of course, yes. FEMA has the power to clamp-down on civil rights.
I think the issue is the main thrust of the government's approach. ACLU seems to think it is a militaristic approach.
That's in a way reassuring because the U.S. military may have a comparative advantage over the U.S. civilian machinery (and civilian thinking), and so there may be an efficiency argument to it.
No doubt martial law would be declared in the emergency. It is a concept mentioned in the Constitution in connection with the right of Habeas Corpus.
Likewise, the state of Louisiana declared a state of martial law after Katrina or what passed for it (a state of public health emergency) which allowed the governor to suspend laws, order evacuations, and limit the sales of items such as alcohol and firearms. Where was the ACLU then?
Maybe they learn from past experience.
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