In order to achieve this you will need to restrict access to the LockLizard Licensing server based on IP address. You will need to install the LockLizard Administration system on your own server and make sure that the server only permits access from and responds only to connections from the public IP addresses you have specified.
So if a user at Company A sent his license file to a user which is located at a LAN/WAN that does not use an authorized IP address then that non-authorized user would not be able to register the license at his own workstation because he would not be able to access the LockLizard licensing server. Please make sure that the IP addresses you specify are PUBLIC so that they cannot be emulated (public IP addresses are ones that are registered with the Network Information Center (NIC)).
If you are using Safeguard Enterprise version 4 and above you can achieve this on hosted and own server systems by using the Restrict IP feature on both a global and user basis to restrict the IP addresses or address range. This works for both the registration and viewing of secure documents.