The Internal Revenue Manual has a rule that covers my issue but the California Franchise Tax Board does not address my issue. So in this case is the default rule the IRS rule? For example, does Calfornia have a law that says the taxpayer starts with federal adjusted gross income and adjustments are made pursuant to California tax law?
Its not just rules, its analogies to and similarities with other similar rules, and then there are cases, and state court rulings, federal rulings interpreting the rules, BOE holdings, State Court Holdings, and much more.
Your question is in the abstract and because it is, I have no way to help you with a meaningful answer.