Outgoing communication barring service in the IP multimedia subsystem

A user terminal comprising:

• an IP Multimedia Subsystem, IMS, client configured to enable the terminal to communicate with an IMS network, the IMS client comprising,
• a conference creation and control circuit configured to create and control an IMS conference involving one or more participants, participants being identified within a conference INVITE or REFER message by respective Uniform Resource Identifiers, URIs, within a URI list, the conference creation and control circuit comprising a response handling circuit configured to receive for from said IMS network, in response to the sending of an INVITE or REFER, a SIP response message including an XML body specifying an Outgoing Communication Barring, OCB, service invocation result and configured to present the specified result to a terminal user,
• wherein the OCB service invocation result identifies one or more barred URIs from within the URI list.