USHL teams have a protected and affiliate lists. These lists prevent you from playing on any other T1 or T2 team. It does not impact playing TIII or Junior A in Canada.
The protected list is primarily made up of kids from last years team and those drafted in the recent Phase 2 draft. These are kids looking to make the club for next season. The current list today going into the tryout camps are at 40 and then have to be pared town to 30 in July and 23 by the start of the USHL season.
Affiliate lists are kids from the futures draft. That list containst 20 kids. This year the affiliate list will be for the most part:
Ten - 02's just drafted
Eight 01's from last years draft
Two - 00's from previous
It's not always the case because some kids are dropped and replaced by kids from the Phase II draft but generally this is what you will see.
If a player is undrafted he can tryout for any team.