The most important word in our military instructions from ATC to an aircraft was "clear".
The implications of using it, were that excluding unknown actions, the request by a pilot to do something was safe to allow.
At various units I controlled at with mixed fast jet and helicopters, there were occasions that we couldn`t see where some helos were ground taxying from. So, after the pilot requested taxy clearance, we replied omitting the word "clear" because we couldn`t guarantee his/her movement in an area we had no control over.
This always seemed to me to be a huge CYA and we asked the crews if they were aware of our missing word and the reason. They all replied that they didn`t really appreciate what we had implemented and perhaps consultation first would be preferable!
Sounds like a plan in any aviation structure to my thinking.