well to sort of answer your question since I don't know the rules in every state's racing commision - I think the most common rule is that jockeys are #1 only allowed to bet races in which they are riding AND #2 only allowed to bet on their own mount. In the more strict states, they have to keep a log of their bets and/or only certain people, i.e., the horse's trainer or owner are allowed to wager for them.
Obviously it would be hard to keep a jockey from giving info to other people like wives, girlfriends, agents and equally hard to prove. I have known people in all 3 of those categories who bet major cash, but the jockeys they were associated with always played it absolutely straight as far as anyone could tell - they would never even talk about betting on their mounts or the odds of horses they rode it was always focused on them being glad if they won or if their horse ran well and they had a good trip. If you asked them about what their wife or agent was betting they usually had no clue.
Actually kind of suprising that there isnt some stories with some jilted lover, ex-wife or degenerate agent who would have squealed on a jockey if they were making bets for them.