Here is the rules from the Mainland site:
The REAL question though is: will the rules be enforced?
Last year alone, there was the example of a 2012 Cashmere Nike Cup player who played for Christs College in the 2012 winter season; and the Cashmere 2011 player who played 2012 Nike Cup and season with FC20. There will no doubt be others. As someone mentioned earlier, 2013 APFA boys (4 that i know of) have been playing in lead up games for Nomads and Waimak and FC20. Not sure whether or not they'll be playing for those clubs this year.