With the new online system you have the power to accept and deny campers. When you login to the camper portal you will see a list of every camper who has requested your camp. If they have paid and completed all the necessary forms you will be able to "Accept" or "Deny" them to your camp.
You can also turn on/off registration for your camp once you think you're full and set the capacity (it's more of a guidline). This helps campers have an idea of how full the camp is. Ultimately though you have the power to let someone in.