You would have to either login with a non-domain account or possibly hack the registry to override the setting being downloaded frm the domain each time you login. I am not sure but if you can get into your registry and search for this registry setting you may have the local admin rights to change it but it would probably revert the next time you login.
Probably the easiest thing is just to have IT remove this from your profile or change your group membership to allow design mode. Although sometimes getting IT to do something is not easy...