Sorry for dragging up and old thread, but I have just been through exactly the same with Thames Valley. FAC initially granted with no condition for fox, but a supervisory condition for deer. Same rifle, same ground etc.
I objected to the requirement as a) it made no sense and b) the condition was not clearly defined and I didn't want to be in breach of it simply through ignorance. During my interview with the FEO the following was stated:
1) He freely admitted that "supervision" wasn't defined by the courts (i.e. did it mean in line of sight, in same wood, at end of phone - he couldn't say and stated it would only be defined if it all went wrong and the courts got involved).
2) When queried how long the supervisory condition would be on (i.e. in months or number of deer shot) he was unable to give me an answer.
3) If I had DSC1 he would grant no supervision, depsite it being a classroom qualification only.
4) I was able to go out on same ground with same rifle unsupervised and shoot foxes (at night if I wanted!).
5) By the FEOs admission, I had met all the legal criteria for grant of a FAC (good reason, temporate & safe).
I questioned the condition and it was passed to the Snr FEO who called me to say the species specific condition shouldn't have been produced and the original FEO had made a mistake. I either had to produce the name of a mentor or someone write saying they had been out with me and I was safe/responsible etc.
BASC got involved, but in all honesty did nothing but delay things sufficiently for me to get out a few times with a local Head Keeper and get him to write me a letter.
I strongly feel that the Police are shirking their responsibility over this issue, and need to get off the bloody fence. Basically, anything which took the responsibility for making the decision away from Thames Valley was acceptable - whether it was a DSC cert or a letter from any FAC holder, they weren't fussy!! It feels a lot like they are doing this to cover their backsides and not for the right reasons of safety or deer welfare.