In the tournament registration tool available on compusport.us (1$ per player that is registered through the system)
You can choose to accept players to create new players or not. (You don't want to allow this if you are a tournament that goes through an Association)
If you want to check if this is turned on or off go to :
Menu > Manage > Tournament Registration > Manage User Registration.
Click on Divisions and Settings.
Then click on Event Settings.
In the pop up, go to Validation Rules section, one if called Can Create New Players.