A method for validating radio resource control (RRC) messages begins by receiving a RRC message at a wireless transmit/receive unit (WTRU) from a radio access network. A determination is made at the WTRU whether the message is valid by applying a predetermined validation rule. The WTRU accepts the message if the message is valid. The WTRU rejects the message if the message is not valid. The message is rejected unless a new transport format combination set (TFCS) is provided, until the WTRU enters a CELL_DCH state, or both.