1. Ways of Enforcing Rules and what is wrong with each
Three parts to the job:
Catch the offender and collect evidence
Determine if he is guilty
Punish him
Criminal law: State actors are hired to do all of it
Enforcers act in their interest, not our interest
Many costs are imposed on others, so may be ignored
And the cop has an incentive to sell the evidence to the criminal
In their mutual benefit
So we need mechanisms to prevent that
Privately prosecuted criminal law: A private actor catches and prosecutes
If his incentive is the reward, he may prosecute someone who is innocent
If private deterrence, doesn’t work when the criminal does not know who the victim is
Out-of-court settlement only works if the defendant can pay

2. Tort Law The victim or his agent catches and prosecutes
Doesn’t work if
The defendant can’t pay—is judgment proof
If the chance of catching and convicting is low
It would cost $2000 to identify and prosecute the offender whose tort cost me $4,000
And I would have only one chance in four of success
The damage payment is doing three things at once
Punishing the tortfeasor
Rewarding the victim for successful prosecution
Compensating the victim for his loss
There is no reason why the same sum should be right for all three

3. Feud System Private and decentralized Problems
The victim catches, prosecutes, and enforces the verdict
Policeman, judge, jury and executioner. Sounds dangerous
Problems
It requires some commitment mechanism, to make me carry out my threat
Unjustified or extortionate claims are limited by third parties
If plaintiff and defendant really disagree about the claim
Defendant has an incentive to resist, which can produce continued violence
So you need some mechanism, such as arbitration
That lets one side or the other give in without looking weak

4. Community responsibility system
Prison gangs, Vitsa, Dia paying groups
Smith vs Hume on established religion
It requires some mechanism to enforce rules of behavior on the group members
Prison gang: Like a government with criminal law
Religious sect: Like norms, ostracism, similar non-violent enforcement

5. Reputational Enforcement
If you act in ways that make dealing with you costly
Other people choose not to deal with you, which is a cost to you
Not to punish you but to protect themselves
Which depends on their knowing who is at fault
If they cannot tell, they avoid both parties to the conflict
Which makes complaining that someone cheated you unprofitable
So you don’t, so reputational enforcement doesn’t work
Which is an argument for some way of lowering information costs
Reputational enforcement depends on repeat dealings
But most of us interact with other people in many ways
If I cheated you in one way, others may distrust me in other ways

6. Enforcement by the Threat of Ostracism
Making it work faces a public good problem
Why should I give up opportunities to associate with someone
Just because other people want to punish him?
Solution: If you associate with him, you get ostracized too
Depends on a society sufficiently isolated so he needs to associate with fellow members
Enforcement of private norms works largely by the same mechanism

7. Religion as an Enforcement Mechanism
Obey the rules because God wants you to
Supernatural pollution that is contagious
Oaths as lie detectors
Divine intervention—trial by combat or ordeal
Leeson argues that, in the Middle Ages, ordeals worked
Most defendants believed in them, so only chose to undergo an ideal if they were innocent
Priests knew that, so mostly rigged the ordeals to acquit
Religious rules are obeyed because
They are right
God will enforce
Other believers will enforce
Test: Are the rules obeyed when nobody is looking
Romani quote implies that they sometimes are not

8. Potential Problems Someone has to interpret God’s will
If someone else, he may interpret it in his interest
If you interpret it yourself
You may decide that what you want to do isn’t sinful
Everyone is a biased judge in his own case
If the reason to obey God’s will is fear of punishment, it only works if
God is really there and punishes, or …
Whether you are punished is not observable by you or others

9. Conclusion
All of the alternative ways of enforcing rules have problems
So which is best probably depends
On the details of the society

10. Incentive to Enforce and the Problem of Error
Rules require an incentive to enforce or they don’t get enforced
But there are also problems with too much incentive
Of two sorts
We may spend more resources enforcing laws than it is worth
And a strong incentive to convict may lead to convicting the innocent
Directly, because someone profits from doing so
Indirectly
The lower the standard of proof, the more guilty defendants get convicted
Also more innocent defendants
We try to prevent that by legal rules for separating innocent from guilty
But it isn’t clear how well that works
The U.S. has elaborate rules for jury trials but
Almost all felony convictions are by plea bargains
How would you estimate the rate of false positives in the criminal justice system?
Apply a new technology to old cases: DNA testing
Several attempts to do that suggest error rates of a few percent

11. Trying Too Hard: The Law of Torture
The original medieval solution was an ordeal: Let God judge
They abandoned that on theological grounds: We don’t get to order God around
Replaced it with a very high standard of proof
Evidence clear as the noonday sun
Two eyewitnesses to the crime
Or a voluntary confession
At which point most criminals could not get convicted, so …
They instituted the law of torture
Once they had half evidence, such as one witness or good circumstantial evidence
They could torture the defendant into confessing
Confessing under torture wasn’t voluntary, so
Stop torturing him, ask if he wants to confess, if he doesn’t torture him again

12. Other Versions
Arguably, plea bargaining in the U.S. has the same logic
Give defendants lots of rights in jury trials to avoid convicting the innocent
Now jury trials take too long to use for all felonies, so
Replace trial with confession, not by torture but the threat of higher penalties
Jewish law was even stricter for capital offenses
Not only required two eyewitnesses, but
Witnesses who had warned the criminal in advance
But the found various grounds for ignoring that requirement
Islamic law requires two witnesses for a Hadd offense
For Zina, four witnesses to the same act of intercourse
But there are multiple alternatives with lower standards: Tazir, Shurta, …
Some schools hold that in Tazir the judge can convict on his own knowledge