People are able to permanently opt-out of communications.
United Kingdom: Telephone Preference Service, a central register for opting out of marketing calls. A similar service exists in the US.
United States: The CAN-SPAM Act of 2003. Requires promotional emails to contain unsubscribe links as well as the mailing address of the sender.
European Union: The Directive on Privacy and Electronic Communications requires consent from the data subject before unsolicited communications are sent.
Australia: The Spam Act 2003 requires data subjects to opt-in to unsolicited communications. These unsolicited communications need to include a clear statement of the identity of the sender and clear opt-out instructions.