Each state is supposed to have a Score Chair that all scores are sent to--scores from sanctioned meets. We have one, I have run for that office in the past. Our state looks carefully at scores to make sure its done right (not saying they don't miss some, but they actively ask gyms for scores and have questioned our owner about transfers from out-of-state). If each state committee was doing the job properly, there would be a lot less gym owners circumventing getting the proper score-out scores.
There is a new rule this year that is going into effect in August that addresses moving back and forth between USAG DP and Xcel, AAU, NGA, etc. It is a step in the right direction, but I think there will be a lot of headaches trying to implement it this first year.