There are, as I see it, two distinct legal issues here, wrapped together, because, its, well, "GUNS!!"
(yes, intentional sarcasm)
The first one is, of course the restriction of lawful arms simply by Gubernatorial fiat, but the second one might be even worse, using an imaginary "public health crises" as the method and authority for the order.
And, lurking behind both is the worrisome fanaticism that says "if we can't get what we want through legal means (the entire legislative process) then its ok to use any means at our disposal to do it." (Executive order, public health order, etc....)
Morally/mentally bankrupt politicians who will not offer any significant solution to the issue but to ban/restrict guns are NOT solving the problem. It is, in fact doubtful to me that they
want to solve the problem, no matter what public statements they make.