You'd use filesystem permission for this. Put your Access database file (both BE/FE) in a certain folder and grant full permission only to that domain group. Your users can then enter the folder,copy the FE to their desktop and link to your BE. Any users not member of the domain group can't access folder and if they did manage to get your FE somehow (by copying other user's FE for example) FE won't work because it can't link to the BE which is still in that protected folder.
Be sure to convert your FE into a MDE or ACCDE to also protect the code and thus prevent users from tampering with the code itself.
