Basically, I want to be able to search for folders a specific user or security group has access to using Windows Search, but I'm unsure if there is such a metadata attribute that can be used, e.g. permissions:[user] (which, obviously, doesn't work)
Whilst this is not exactly 'searching' for ACLs there are ways of displaying this information. One option would be to use DumpSec from Somasoft.
Another would be to write a batch file calling the internal Windows command 'Cacls':
Or alternatively create a script in Powershell for the same purpose: