This has always been the policy but schools have become lax in the vetting process. The way things are today I doubt the school wants to deal with the parent of a good player who is told he can't play in the game and not nominate them..
I believe what swag is talking about after last years incident the DFRC has asked the Coaches, AD's and Principles to take the vetting process more seriously. I do know there were some good ,even all state players that Caravel didn't nominate do to character in the past. There is other examples too, Last year Sallies had a lineman that was on the roster when it came out but did something between then and the game , dont know what , but it got him booted from the squad..