You’re right that majority rule is not sufficient by itself, but public opinion should be given at least some weight in a representative democracy.

The US Constitution grants states the right to enact laws that protect the general welfare, and of course gives courts the authority to interpret the law. More specifically regarding public health, the 1905 Supreme Court case Jacobson vs. Massachusetts upheld the power of states to enforce mandatory vaccination laws (https://en.m.wikipedia.org/wiki/Jacobson_v._Massachusetts):

> ”real liberty for all could not exist under the operation of a principle which recognizes the right of each individual person to use his own, whether in respect of his person or his property, regardless of the injury that may be done to others”

In general, John Stuart Mill’s harm principle is “far and away the best known proposal for a principled limit to the law” (https://plato.stanford.edu/entries/law-limits/#cand), and it is a core tenet of liberalism. The famous bit is:

> ”That the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others.”

This principle is echoed in the party platform of the US Libertarian Party:

> ”Criminal laws should be limited in their application to violations of the rights of others through force or fraud, or to deliberate actions that place others involuntarily at significant risk of harm.”

So if masks only protected the wearer, then a case could be made that mask laws are in violation of this principle. But because masks help limit the spread of a (frequently asymptomatic) disease from myself to others, it’s reasonable that states can require me to wear one in situations where it protects others.

As for the enforcement question, I’d draw a comparison to speed limits. These laws tend to be loosely enforced, yet they guide the general expectations/behavior of drivers. In practice, enforcement is reserved for repeat and extreme offenders. Partial enforcement can induce optimal behavior in an economic/game theoretic sense (if probability of being caught * cost of being caught - cost of following the law > 0, then compliance is optimal). Since the “cost” of wearing a mask is negligible (everyone has one already since you can use any face covering, and the only cost is minor inconvenience or embarrassment), enforcement does not have to be very consistent to induce compliance. That said, uneven enforcement of laws is clearly a major problem in our society (that disproportionately affects minorities).

For mask laws, I also think it gives air cover to both business and individuals. You’ll notice businesses pointing to mask ordinances (“welp, thems the rules” etc.) on their signage and such. Then, enough people comply such that it becomes socially enforced—people generally don’t like to be the odd one out. But in practice, I think you can go virtually anywhere in America right now without a mask and the worst thing that is likely to happen is that someone will politely ask you to wear one and come back.

So if you are not anti-mask but are concerned about genuinely authoritarian action, there are current examples to denounced (e.g. stoking political violence against opposing politicians [see Gov. Whitmer], undermining election integrity, state-sponsored misinformation).