Action movies often show fights in complex environments like factories, ships, kitchens, warehouses, or construction sites. In such cases, whomever knows more details of that environment can have big advantages in the fight. However, when people instead try to arrange a “fair fight”, they usually choose simple environments that combatants can know similarly well, like an empty flat walled square or circle.

Lawyers often fill their offices with big shelves full of law books. As if to say “Law is a vast complex machine you wouldn’t want to mess with without access to an engineer like me who knows all its details.” Or more relevant, “The arena of law is as complex a place for a fight as is a factory or kitchen. You don’t want to fight there without a warrior like me who knows all those complex details.”

However, the essence of law is for a judge to hear A complain about B, and then to issue a ruling to reward or punish A or B. And the main point of such law is to induce better behavior via shared expectations of such rulings. For that purpose, what matters about the law is those shared prior expectations; further legal detail beyond that has little social value.

Actually, added legal complexity and detail can hurt, by tempting people to learn more legal details in order to gain strategic advantages. Just as warriors fighting in a kitchen would need to learn kitchen details, people with possible legal conflicts can need to learn about arbitrary legal details, or to hire lawyers who learn them, even if those details do little to help guide prior actions by A or B.

Imagine that two people will hold a verbal debate in some physical space. Law without needless details is like the debaters sitting on a simple couch to do their debate. Such a couch has little other structure besides that which is needed to coordinate their locations and orientations. Which is good.

Now imagine a couch with lots of little pockets holding weapons or controls to make the couch poke people, change shape, get hot, or make noises. Something like a car. If you were to be in a debate on such a complex couch, you’d want to invest in learning those details. For example, you might be able to poke your opponent out of view at just the right moment. Even though that is a social waste.

Is a minimal couch-like law possible? Consider juries. Imagine there is little formal law, so that juries can rule most any way they choose. In this case legal expectations are just expectations over jury rulings. So if A and B know the community from which jurors are chosen well enough, then they know that they have shared legal expectations. And they know that there’s not much either of them can do to gain more info on that. Their law is a couch, not a car.

Of course it is not enough just to have shared legal expectations; one also wants those expectations to do well at taking into account situation details known to both A and B. Thus one problem with a simple jury system is that random juries many not know important situation details that are known by both A and B. So each pair A and B might prefer that a case between be judged by a jury chosen from a community closer to them, so that this jury knows more of their shared context.

But you also couldn’t pick jurors who are too closely connected to A and B, as these might not be willing to function as independent jurors. So, for example, if A and B are both in the movie industry, it might make sense to give them a jury from the movie industry, who could then understand movie practices. But maybe not jurors who are currently working on the very same movie as they.

150 years ago, the US had something closer to this simple jury system, as stated laws were few and vague, juries made most decisions, lawyers were cheap and less often needed, and plea bargaining wasn’t yet much of a thing. Since then, US law has accumulated far more detail. Yet little of this detail seems to be an adaptation to a more complex world; most is just random. And we must pay lawyers who learn this detail if we hope to win at court.

Worse, regulations greatly restrict who can be a lawyer, slower more expensive legal processes add to our costs, and few of us have sufficient assets to pay if we lose. Thus US law has rotted in a great many ways. When will we notice that, and consider big changes?

By the way, one feature that we might want in a legal system is an ability ask it for prior approval for behavior. “Would it be legal or not-negligent if I did it this way?” And you might hope that a very detailed legal system could at least offer this advantage over a simple jury-based version. You’d just look up the relevant detailed law. But in fact our very complex detailed legal system doesn’t offer this feature. You just can’t ask what acts might be legal; you can only do stuff and find out later if you are punished.

Added 11a: Jury decisions can vary. To reduce the impact of that in particular parties, we could  have the consequences for them be set by prediction markets on jury decisions. Those market predictions would be far more consistent across cases.