Such cases include for example the application of tax law: Yes, it is complex and maybe cannot be automated entirely. However, even today, computer programs handle a large percentage of the arising cases automatically in many governments, and these programs often already have automated mechanisms to delegate a certain percentage of (randomly chosen, maybe weighted according to certain criteria) cases to humans for manual assessment and quality checks, also a case of rule-based reasoning. Even fraud detection can likely be better automated by encoding and applying the rules that auditors already use to detect suspicious cases.
The issue today is that all these rules are hard-coded, and the programs need to be rewritten and redeployed every time the laws change.