I got called out last week for cleaning my ball mid-game during league, even though I was using Remedy cleaner, which is approved for use ANYTIME during competition, and I told him so. Regardless, the other person was sure he was right, and since I didn't want to cause a big stink and wasn't absolutely 100% sure I was right, I just let it go. So now, I carry a copy of the USBC rule and their list of approved cleaners in my bag so I can whip it out if the situation ever comes up again. BTW, the individual that complained is the Pres and high average in our league, so you would think he would know the rules. (Our league follows USBC rules, with no variations).
Also, remember that leagues and tournaments can have their own specific rules that might differ from standard USBC rules, but if so, it should be stated in the league or tournament rules. Good idea to check, especially in tournaments.