Use the dladm delete-phys command to remove a datalink from the system.
Removing a datalink is only loosely connected to the removal of a physical NIC. For example, if a physical NIC is removed from the system, the datalink configuration that is associated with that NIC remains because the software layer is no longer bound to the hardware layer, as described in Comparing the Oracle Solaris 10 Network Protocol Stack to the Oracle Solaris 11 Network Protocol Stack in Transitioning From Oracle Solaris 10 to Oracle Solaris 11.2 . Thus you can still use the datalink configuration on a different underlying physical NIC by assigning that datalink's name to the other NIC's associated link.
If you detach a NIC without replacing it, and you no longer need its datalink configuration, then you can delete the datalink as follows:
# dladm delete-phys datalink