This disclosure describes techniques for dynamically changing a user authorization with a service provider during an ongoing user session. The changing user authorization may be used to address changing confidence in an identity of a user consuming a service provided by the service provider. The changing user authorization may also be used to adjust a scope of a service to which a user has access. The present techniques may allow single-sign-on type protocols to accomplish the flexible and dynamic change-of-authorization functionality of some traditional protocols to handle ongoing client-server sessions, rather than simply revoking authorization for access to the service. For this reason, the present techniques are able to integrate advantages of traditional protocols with newer, single-sign-on-type protocols.