That is a State Highway. Legally, this is like a roadblock on some random state highway. This is why you don’t let medical idiots dictate policy.
Notice they didn’t say block entry they are using the carrot not the stick here. Locals will tell you in peak season the wait for a ferry can be 3 hours or more in line moving to the front of that line is a big carrot. They legally can’t stop people from boarding but they sure can let people line jump boarding is up to Captain he is the law on any vessel no matter how small or short of the ride.