Few people will question what police are supposed to do. But some may be unsure about what they should not do.

And if cops themselves do not know where the line is, the consequences could be disastrous.

Two men were reportedly detained recently by local police in Henan province and the Inner Mongolia autonomous region for exposing online how their local governments illegally occupy farmland.

The man from Henan was working in Shanghai when police officers from his home county Lingbao caught him and brought him back. He was charged with libel against the county government and detained for eight days before he was released.

His counterpart from the city of Ordos, Inner Mongolia, was arrested and sentenced to one year in jail for doing the same thing.

He appealed to a higher court but only got another year in prison.

The man from Henan was soon acquitted because of pressure from public opinion both online and in the media. The provincial police chief apologized to him online. He is also set to get compensation for being wrongly detained.

His counterpart from Inner Mongolia was not that lucky and is still serving his jail term.

In both cases, police have apparently turned out to be a tool of the local government to tackle unfavorable opinion, a role that might go against the Constitution and relevant legal codes.

Public security departments at different levels are supposed to be under the leadership of their corresponding governments. But they also have their own rules to follow.

The two men's actions in the latest cases are supposed to be protected by the Constitution, and they have their rights to speak against the government.

Bending laws by judicial organs such as public security departments should be the last thing to happen in a country with a sound rule of law.

To our great comfort, the Internet and other forms of media have played a supervisory role against such violations. The pressure from them has also prevented the public security department in Lingbao from continuing their infringements on the rights of citizens.

The public security departments need to learn from both cases where to draw the line. It is inspiring that media of different forms and public opinion on the Internet are playing an increasingly important supervisory role over these cases.

This role should become an indispensable factor to increase the awareness of local governments to know where the line is.

(China Daily April 21, 2009)