Because the NCAA doesn't give a toss about a legal case against you or any other fan doing something that is clearly legal, as is giving money to an athlete (as long as it is below tax limits, or setting them up with a willing companion for the evening. What they do care about is a ton of rules they have in place about undue influence on HS kids looking at scholarship offers by 'boosters' for any of the schools involved and they have a very broad definition of what a booster is. The students are also barred from signing contracts with agents or making a profit from participating in their sport prior to completing their athletic eligibility which are all clearly legal actions, but doing so makes them ineligible to compete in NCAA sanctioned events.
They will not be coming against you, or some booster, but all NCAA schools belong to an association and have agreed to abide by the rules imposed by the association on their athletic competitions - so they will go after the school and by association, at the potential recruit. They can ban a school from offering an athletic scholarship to a particular student and if the school defies that ban (as they have a legal right to do, they can sanction the school from participation in NCAA competition which by agreeing to the be a member of the association they have agreed to be governed by. Some of the rules of the association impose standards for behavior for the school's fans and a responsibility of the school to police those fans to the best of their ability. And the proceedings of the association are not subject to the same standards as exist in a court of law, and the laws of this country recognize that those standards do not need to - check out deflate gate for a case in point.
