AFAIU, the French Tax Code is effectively defined in terms of an algorithm. There was a recent HN thread (https://news.ycombinator.com/item?id=25208853) on a new open-source compiler for the tax code (https://arxiv.org/abs/2011.07966). The paper for the compiler references some interesting literature on the computability of legal codes. For example,

> [U.S.] tax law drafting style follows default logic, a non-monotonic logic that is hard to encode in languages with first-order logic (FOL).

Tax laws are hundreds to thousands of pages each. The complexity is intentional and not accidental. Many carve outs are specifically created for special interest or to target certain constituencies.

Edit: referring to the US