A method for enhancing User Equipment (UE) handling in a limited service state over non-Third Generation Partnership Project (non-3GPP) access is provided. A UE sends a REGISTRATION REQUEST message or a SERVICE REQUEST message to a Public Land Mobile Network (PLMN) over non-3GPP access. The UE receives a REGISTRATION REJECT message or a SERVICE REJECT message from the PLMN over non-3GPP access. In particular, the REGISTRATION REJECT message or the SERVICE REJECT message indicates serving network not authorized. In response to the reception of the REGISTRATION REJECT message or the SERVICE REJECT message which indicates serving network not authorized, the UE enters a limited service state and performs a non-3GPP access network selection.