A recent blog post has caught my attention. It describes another usual day in Jakarta, complete with major traffic jams and motorcycle drivers using the curb lane. The writer, a pedestrian, says he was in a fight with a motorcycle driver who wanted to pass him and kept asking him to step aside.

Of course, the request was ridiculous. The lane has always been reserved for pedestrians, and they don’t have any legal obligation to let motorcycle drivers use it. Just when the fight was about to turn physical, a police officer came to break things up.

At first the officer scolded the driver, saying he was violating the law and could be fined. The driver simply replied that he would accept the punishment as long as the officer also fined other motorcycle drivers using the curb lane, and there are many of them.

Upon hearing that, the officer turned and instead scolded the pedestrian for his refusal to let the driver use the lane. It was a perverse result, showing that the officer was regrettably taken by the driver’s misleading argument.   

We hear this kind of argument for fairness all the time. If you want to punish me, you should also punish the other people who are involved in the same crime. Or if you want to punish me, you should show that you’ve never done the same thing yourself. Is this argument valid when we’re talking about law enforcement?

The answer is no. From a legal perspective, I’ve never seen any serious legal philosophers who support the idea that in order to make a valid legal enforcement, legal enforcers must be saints and ensure that all people who commit the same crime will be punished at the same time.    

From an economics point of view, it would simply be inefficient to have that kind of rule. Imagine the costs if we had to ensure that all legal enforcers possessed the moral capacities of a prophet, being a perfect person who absolutely adheres to the highest standard of moral and religious principles. Where can we find such a great  person?

Pakistan would be good case study. Pakistani legal officials, who believe they act in accordance with the correct version of Islamic law (unfortunately, it’s not correct), have established a strict rule for becoming a witness in homicide cases. People can only be witnesses if they have certain moral qualities, which include, among others, praying five times a day, never lying and maintaining good hygiene.

The result? No one has ever been punished for murder under Pakistani Islamic law. Thankfully, that does not mean murderers can run away from their liabilities, because Pakistani legal officials still use the witness standards established under the English law, which is also applicable in Pakistan. But you see the point.

When police officers are dealing with cases like the one I describe above, they should realize that they can in fact punish a motorcycle driver even if they don’t do the same to other violators. By punishing one driver, they can set an example that they’re going to enforce the law, even if it’s in a random or selective way.

And such enforcement would be efficient. There are costs for law enforcement, and the optimum crime level might not actually be zero because at certain point, the cost for law enforcement might outweigh the benefits that we expect from reduced crime. This is called diminishing marginal returns.

Of course, there are situations where we might be required to increase the law enforcement costs for specific crimes (say, corruption). But for traffic violations? Having random or selective enforcement in this case would be sufficient to give the correct signal to violators.

Sometimes, uncertainty is effective to deter crimes. If you don’t enforce the law at all for traffic violators, they’ll think it’s fine to commit a violation as long as everyone else does, too. But if they know they might be punished, even if it’s just a possibility and not 100 percent guaranteed, they will think again.

Such uncertain law enforcement will increase the costs of violation and make people more likely to comply with the rules. That’s why law enforcement is still necessary, even when the process is random or selective. So next time a police officer faces a similar case, he should just fine the guy and say to him: “Well, tough luck, sir!”