local administrator account has full access on domain file server

We have some computers that, when you log in with the local administrator account, it has full access to all the file folders on the domain server. All of these folders have specific NTFS permissions assigned to them, each of which is an active directory user account on the domain.  How can a local admin that doesn't even have an AD account on the domain get full access? We really need to take that away from that account.