You can only lock down a city in a dictatorship. So I certainly would not approve of this behavior. Additionally any speculation about the effectiveness of the quarantine is futile in my opinion.
What? US state and federal emergency responders have plans and tools for locking down a city, too.
They can lock down some roads or a building and maybe the air space, but anything on a larger scale is unrealistic. If someone did this in a western democracy, you can be sure those responsible would be on their last term after the initial hysteria waned.