[btilly]

Legally, is this possible in the US?

Great question.

The Constitution is very clear that ultimate authority about Interstate Commerce belongs to Congress. States cannot bar travel from other states.

HOWEVER there is legislation enabling states to impose quarantines on people coming from other states. https://www.nytimes.com/2020/04/10/travel/coronavirus-us-tra... has information about such quarantine rules currently in place.

So stop travel, no. Make it difficult, we're going to see a lot of that.