As a service provider, you can mark a channel as open or closed for registration. When a channel is closed for registration, self registration is not possible.
The service provider sets the global default value of the parameter allow.signup to true or false in the portal settings to allow or disallow signup. During channel creation, this value is picked from the global settings defined for the portal. You can override this setting during channel creation for any specific channel or you can edit the channel settings at any time. The default channel always reflects the value (of allow.signup) that is globally defined. For more information on configuring portal settings, refer to Configuring portal settings.