Outside of requiring boosters to perform@31 background checks not a whole lot you can do. If there's a positive taxing the money could help fund compliance offices. The more resources the more they can monitor players. But there's no way you can stop a "shady" individual from getting to these kids. But you can reduce the likely hood. If I can make 50,000 in legal booster money I'm less likely to take money to risk my college career and freedom doing something illegal.