They can decide they have reason's for security threat and or weather and stop all commercial trafiic.
What I am asking if it is like here? The Port captain has absolute authority in what regards safety and sometimes, if he finds it adequate, he can, for safety reasons, close the port not to all commercial or pleasure craft but just to some types of boats.
For instance in Figueira da Foz, a marina on a river near the mouth and also a Port, the Port Captain frequently closed the port to boats smaller than 10m, when the waves on the bar would make dangerous the crossing of the bar for those boats. I am not discussing if he is right or not. If he finds so his ruling is final. He can do whatever he pleases in what regards safety if he finds it justifiable. Of course if he takes absurd measures he has to justify himself to his superiors, but only later.
Well, for you to understand better, here all Ports are regulated in what regards security not by civilians but by navy officers. The Captain of a port is always a Navy officer and I guess only one of those would have the balls to say that the Bounty was not authorized to leave port. Or am I wrong?
edit: I guess Nolatom replied to my question but that need to go till the Admiral seems not very practical on what regards effective measures when they are needed.