In NE it is best to buy your fish and keep your receipts locked in a fire proof safe. State regulations apply if the state provides the fish, if your pond is connected by inflow or outflow to other bodies of water where state fish "might" gain entrance to your pond, state regulations also apply if you cannot provide receipts as proof of purchase. If you buy your fish, keep your receipts, if there are no outflow or inflow issues you are free to ignore state regulations and harvest your fish as you like.
Our current state regulations were changed for 2009 and all LMB under 15" are now catch & release, private ponds included. Special waivers are now required from the state if you want to cull any overabundant LMB under 15", that is unless you have receipts for all your fish and no inflow or outflow issues.