Yes, KQ...I'd say that TDA #24 covers your question. There is no mention of a penalty but, any player that does not comply with your rules is subject to penalty. Remember, there is a difference between a player who accidently might have a "dirty stack" with one or two chips misplaced, and a player who intentionally shuffles mixed denomination chips together.
Knowing the habits and history of your players is helpful. A new player should be considered less likely to draw a penalty than a repeat offender, or an experienced seasoned player. I'd say that, one warning should be enough, wouldn't you? If they don't listen, hit them with the penalty.