OK. So I want to restrict access to local users and directory users that are a part of group FSLocalUsers. This group has 4 higher-level groups within it. No individual members.
I don’t want to use SACLs to restrict access, because all that happens is the “shaking window”, no actual error message, ergo users have no idea why they are being denied access.

How do I check if a user is part of this group, since dscl won’t show it?