“Pan-secessionism” seems to be increasingly common in practice. Examples include 2nd Amendment counties, sanctuary cities, autonomous zones, federal drug law nullification, refusal of lockdown orders, etc. As well as other forms of more serious “direct action” like torching enemy military outposts and star chambers, or looting corporate feudal plantations.
I could conceive of some kind of public health emergency where dramatic quarantine measures or some other far-reaching response would be justifiable based on a pragmatic assessment of the circumstances. I approved of Obama’s banning flights from African countries where the Ebola outbreak occurred in 2014. Ditto Trump’s ban on flights from China. Shutting down or restricting transportation systems with lots of people packed together during a pandemic might be justifiable, or large gatherings like stadiums. But generally speaking, I think people should individually look out for their own health, and groups should practice freedom of association. For example, if a restaurant wants to require masks or take peoples’ temperatures before they enter, fine. If people don’t want to wear a mask or have their temperature taken, they can go elsewhere. And other folks can also refuse to patronize businesses that don’t implement health guidelines.