You can stop cross-realm authentication between your realm and a trusted realm by doing one of the following:
Disable the trusted realm. This action prevents your realm from receiving authentication requests from the trusted realm. Trusted users are not deleted and configuration data is not removed. If the trusted realm disables your realm, no cross-realm authentication can take place. This action is easily reversible. You can reestablish the trust relationship by enabling the trusted realm. For more information, see Enable a Trusted Realm and Disable a Trusted Realm.
Delete the trusted realm. This action deletes all trusted realm configuration data and trusted users from your machine. This action is not easily reversible. If you want to reestablish the trust relationship, you must add the trusted realm again. For more information, see Delete a Trusted Realm .