I am not clear if the proposal is referring to all of New York State or just New York City, from John Solomon, Just the News:

[President Donald Trump] “We’d like to see New York [City?] quarantined because it’s a hotspot — New York, New Jersey, maybe one or two other places, certain parts of Connecticut quarantined,” Trump said as he departed the White House.

Maybe POTUS can insure that the National Guard can detain New York City Mayor Bill de Blasio, and escort him to his quarantine facility?  No New York politician has done more to spread the Chinese Wuflu virus than de Mayor.