Ok, this is a spectrum.

How far along the spectrum does the emergency need to get to justify a lockdown?

For example

- The Black Plague which killed 30%~ of Europe. At what point would a lockdown be justified?

- Germany just invaded my northern border. Again. Am I allowed to force my residents to turn their lights off to avoid bombing?

Rights aren't universal, and no serious person argues this. There is always an emergency that's bad enough.

The question is 'what is bad enough' and this has no scientific answer. The answer is up to the government of the day, and the population who can decide whether to turf that government.