If you are using a wireless 802.1X network, there is no way to do this unless they have some way to configure 802.1X credentials. If you are just using a captive portal/MAC authentication, then you can create a new end system list of those MAC addresses with the appropriate ownership in the description and create new rule to allow those MAC addresses onto the network. If you want to allow your users to register their own devices on, you can look into the self-registration pages within NAC.