DHCP – Active Directory

Does anyone know if it is possible to block DHCP requests from being processed to machines that are not listed in Active Directory.
My issue involves rogue machines coming into my network without permission..they see an empty outlet and just plug into it. We have a lot of vistitors in our building.
Maybe I am attacking this problem the wrong way but I would think you can block DHCP requests if the machine is not a member of the current Active Directory Computers.
If anyone knows how to do this or of another way of rogue machines plugging in, it would be greatly appreciated.

Doug Kasdorf
Network Administrator
Oceanworks International Corp