A simple "Is code law? Nah, it's more complicated" governance model... 
Let's start with the most layer-neutral expression of a transaction as an exchange of objects of value (a.k.a. assets) as the building block of economic interaction. Each of the four layers has subtly reinterpreted this definition to suit their own objectives.
If you want, we're starting out at the top left, the current model of a legally incorporated enterprise as the standard model of production. A "nexus of contracts"...
Contracts are the padded envelopes for commercial transactions, starting with the incorporation as a legal (typically for-profit) entity. "Padded" bc 1. contracts can govern more than one transaction, and 2. they come into being as distinct entities under special circumstances.
Our simple example of a simultaneous transaction establishes a contract by default, but contracts only come into being as distinct entities when there is a future-facing element to the transaction. That's why contract is usually defined as an exchange of promises.
This is also why the modern corporation, represented by the stack on the left, is a legal entity more than an accounting entity, and more than a bundle of processes running on a bunch of computers.
A legal contract enables the financing of an enterprise in a world where parameterization, measurement, or even observation are hard, costly, incomplete or asymmetric. A contract enables a participant with an accounting advantage to commit themselves to not abuse that advantage.
That's not only true for the multitude of commercial contracts a company enters during its lifetime, it's particularly true for the raison d'etre of a company: to provide funding for entrepreneurial effort that, in the future and under fortuitous circumstances, creates a return.
So the legal layer allows us to undergo and finance all those endeavors that aren't perfectly accountable or not perfectly based on trust. Which is pretty much all of them. So the steep task of code-is-law based efforts is to improve on this function, and not just assume it away.
The accounting layer is probably the most crucial layer, not only bc the core balue proposition of a blockchain, to safeguard against double-spending is essentially an implementation of the accounting equation, debit = credit.
The other crucial thing it does is to link the verbal, reasoning-based legal layer with the quantitative, proof-based process layer, and in turn, stated intent with measurable outcomes.
