A privacy enforcement engine conducts a process that evaluates user privacy preferences against the privacy policy of a service provider. The engine works in conjunction with an identity selector. The identity selector filters user identity information cards to determine which ones satisfy the requirements of a security policy. The engine identifies privacy preferences that are relevant to the user identity information specified by the successfully filtered cards. The engine evaluates these privacy preferences against the privacy policy, to provide its own filtering operation relative to the exercise of privacy controls. The cards that pass the filtering operation conducted by the engine are deemed available for disclosure.