The tough challenge China faces in its endeavor to build a society based on the rule of law can be seen on the ground as well as below it.

An apt example of this challenge is the Shanghai subway system, where passengers entering the platforms are supposed to put their bags and backpacks on conveyor belts for security screening. Each machine is staffed by at least two people, one monitoring the screen and the other reminding passengers to get their bags screened.

But, as I have noticed on my many subway trips over the past few weeks, most of the passengers simply disregard the rule. And yet the people manning the machines do nothing but let them proceed toward the platforms. On several occasions, I was probably the only one to put my backpack on the conveyor belt, and once I saw the man monitoring the screen was dozing and didn't even look at the screen to see what was in my bag.

The security procedure, imposed during the Shanghai 2010 World Expo against a possible terrorist threat, is no longer working. Security today is too lax to prevent people carrying dangerous stuff from entering the stations.

But does Shanghai still need security screening when New York City and Washington DC, always on high alert, don't have them? The point is that since Shanghai still has a security rule, the city authorities should enforce it with a strict hand.

The situation is no different in Wuhan, Hubei province, and Chengdu, Sichuan province, where local police have been cracking down on jaywalkers and moped-riders who ignore traffic lights and rules. Surprisingly still, reports say that many people who were stopped in Wuhan and Chengdu yelled at the police officers, some even using abusive language. In many countries, such people could be arrested for obstruction of justice.

In October 2011, I saw how New York police spent hours cuffing some 700 Occupy Wall Street protesters marching on Brooklyn Bridge. At first I thought the police officers would not make such a big arrest. But the New York Police Department seems to believe that people who break the law by marching on car lanes should be dealt with accordingly. Despite my dislike for the heavy-handed police those days, I respect the fact that laws should be followed by one and all and on all occasions. Or else, cities will have traffic as chaotic as in Shanghai, where vehicles turning left or right often put pedestrians' lives in danger.

Another violation of the law is evident when one enters a place with "No Smoking" signs in China only to find many people puffing without a care. The poor enforcement of smoking ban in public places is the main reason why China has failed to honor its commitment to the World Health Organization's Framework Convention on Tobacco Control.

Why so few people have been punished despite the country's waterways being severely polluted? Why have the people responsible for dumping dead pigs in Huangpu River not been punished for contaminating the source of drinking water for 20 million people in Shanghai?

China has enacted enough laws in the past three decades, including those to deal with the above violations. However, few seem to know who should enforce them and how.

Laws not enforced are worse than not having any at all because it sends the wrong signal that people don't have to take laws seriously. And if people think they can get away with violating laws, the so-called rule of law will remain just a lip service.

What is urgently needed is a mechanism to supervise the law enforcement agencies in order to ensure that they perform their duties of implementing the laws formulated in the past three decades, failing which they should be pulled up for dereliction of duty.

The author is deputy editor of China Daily USA. E-mail: chenweihua@chinadailyusa.com