Any formal system can either be consistent or complete - not both. Therefore, you will always need an oversight to check for most individual legal cases.
Furthermore, oversight wouldn't necessarily yield any further insight even if it were. Humans aren't extra-logical, we have similar limitations.
The world is what is the case.
We humans are often interested in something else.
The very basics of a legal system are consistency (fairness) and completeness (coverage). Are you making an argument against these two basics?
In particular, the tradeoff between soundness and completeness only holds for those mathematical systems which can internally encode peano arithmetic (naturals, addition, multiplication, first order logic)
Therefore, to invoke the incompleteness theorem, you need to prove that a legal system is powerful enough to encode arithmetic, which to me at least is not obvious.
There are many systems that are both consistent and complete, but are just not as expressive.
You are using words that have a very precise formal meaning into a completely different (informal) sense. Probably this is the source of your confusion.
Results in mathematics, logic, and philosophy have provided undisputed evidence that you can’t reason formally about human ethics.
You’re responding to someone who is correct but made the assumption that you’d be familiar with the field of study and the results.