I don't know about "Legal" in all situations. I do know it has been done at some tourneys - not the large ones. At State, I know it is not allowed (except for a 6U wrestling 8U). In the cases where I have seen it done, you usually have a very good wrestler who would not get a lot of competition at his "natural" age/weight, so he does both brackets to get some competition. Usually it is understood that one bracket won't wait for him/her to finish another match, or there may not be much if any "recovery" time between the matches. I think it is usually just a decision between the wrestler's coaches and where they are wrestling if they will allow a wrestler to enter two different brackets.
