I imagine it's not so much turning a blind eye as not having the resources to deal with it, given everything else that is going on, not to mention budget cuts and lack of officers. In the great scheme of things it is bound to be a low priority.
It would be very hard to prove whether a hunt was drag hunting or on the trail of a fox until one was actuallu caught.
Given the limited resources of the police and the far more important issues requiring police assistance, I would think trying to catch a hunt in the act of hunting and killing a fox would be low on their list of priorities.