Originally Posted by
ignorantAndroid
I may be mistaken, but my understanding is that the controller doesn't really have the option to deny visual separation. The regulations don't mention any response except 'approved.' The word 'approved' does seem to imply that it could also be denied, but there's no mention of how, when, or why that would be done. Even if they do have the option to deny, as far as I can tell there's no guidance on how to make that decision. Obviously there's no way for a controller to know whether a pilot truly has the correct aircraft in sight.
The system works on trust, a lot of things in aviation require trust.
Here, the helicopter pilots had obviously routinely been lying to LC (and getting away with it!), so the system broke down.