Laws past are often changes to legal code, they often soon have other code intertwined with them. How do you expire code automatically, do all dependent changed

Laws past are often changes to legal code, they often soon have other code intertwined with them. How do you expire code automatically, do all dependent changed also have to expire? How do you track the dependency tree? Horse trading is an aspect of compromise: you want A, I would rather not; I want B, you would rather not; so we agree on A & B.