I mean, it's really not. In times of emergency, the government is granted pretty sweeping powers to deal with problems, be they disease, war, civil unrest. Any constitutional challenge here would just have to undergo intermediate scrutiny from the courts and the government would have to 1. show an important government interest that is 2. achieved by means substantially related to that interest. The important interest is public health, and the preservation of American lives, and the means are via quarantine. The lockdowns suck, but from a legal and constitutional standpoint, unless your state constitution says otherwise (which I highly doubt) they're allowed.