It's very difficult to police.
Fell running isn't a navigation race but it is a test of fell-craft, and the ability to navigate yourself along the course is an intrinsic part of Fell Craft, IMHO.

... or run around a 400m track. Saves money on flags.
Geoff - I'll be sure to send you all my road/track results from this coming summer so you can include them in the weekly Pennine mailshot!