Wheelies on Private Property Illegal?

[Bamaguy]

So a close group of friends and I love to do wheelies on our motorcycles but dont like the risk that doing them on the streets brings, so we practice in a closed down warehouse loading lot. We are going slow and in a controlled area where the owners dont mind since we keep it clean (sweep, pick up trash, etc.) and it has been closed down for years. It is not off a main road so we are not distracting anyone. Anyways a bunch of cops swarmed in tonight and said that they could write us wreckless driving tickets even though we are not on public road ways. I am wondering if they were just bluffing because they have nothing better to do or they are actually telling the truth and cut us a break by not writing any tickets tonight. This is not the first time they have come out but it is the first time they have threatened us. Thanks for any help guys.