Policy editing

A client of mine has been messing about with the local policy on his member server.
He has turned off inheritance so group policies won’t override local policies.
And locked down all the local groups including the administrators group and the domain admins group, has set both of these groups so that they can’t logon interactivly.

So I can’t logon as an administrator or a domain admin but need to be an administrator to enter the policy editor program to reset everything.

Please dig into this very deeply as I don’t want the answer to come back as a re-build.

Many Thanks.