I would personally would say that if a university has put time effort and money into training a player then the player should have to sit out to pay the price of transfer unless:

-There is a proven family hardship (submitted to an unbiased counsel to determine) or

-The head coach leaves (tempted to say the original coordinator of your recruited position too) or

-Something else really important I haven't thought of.

That means if you put something into a kid before he went on his mission then he needs to sit but if all you did was get him to say he would play for you then he is not disadvantaged for no reason. The minute a kid steps onto a campus as a student athlete he or she should have some responsibility. Otherwise what is owed to the university?