How is it worded? Does it require a air rifle that shoots at 1000 fps, or one rated by the manufacturer at 1000fps or better?
Maybe a request for some clarification on that, channeled up through the Consevation Officers, or whoever will be doing the enforcement.
If they want velocity in real life, most of the 'rated' airguns will fail unless used with very light pellets (no energy retention, poor accuracy, etc, problems) but if 'rated' is all they want,, then you can pick and choose the pellets that work best, though they will like as not, be slower.
Cheers
Trev