A client-side user agent operates in conjunction with an identity selector to institute and exercise privacy control management over user identities managed by the identity selector. The user agent includes the combination of a privacy enforcement engine, a storage of rulesets expressing user privacy preferences, and a preference editor. The editor enables the user to direct the composition of privacy preferences relative to user identities. The preferences can be applied to individual cards and to categorized groups of attributes. The engine evaluates the proper rulesets against the privacy policy of a service provider. The privacy preferences used by the engine are determined on the basis of specifications in a security policy indicating the attribute requirements for claims that purport to satisfy the security policy.