I have someone asking if they can block outbound calling from a specific extension to 911. In other words, they want the phone to be able to call internally, but not dial externally, including 911. So 2 questions.
How is this achieved?
The better question is, Is this even legal? (restricting dialing to 911)
There are things you can do - for example, there are a bunch of new settings that allow for outbound 911 calling to ring a central office phone. You can also deal with ‘the problem’, assuming it’s a specific employee or phone, administratively.
Blocking access to 911 is going to end up badly. Monitoring 911 activities, especially from a ‘specific phone’ is probably a good idea either way.