Two college students used their phones to video a police officer kicking a suspect when he was unable to open a door on a police car. Because they refused to hand over their phones to the police, the two students were taken by force to a nearby police station, where two police officers slapped their faces and beat their buttocks with batons.

The horrible photos of their bruised and swollen posteriors were widely circulated online. The city's public security department confirmed the next morning that the student's allegations of being beating were true and the police officers concerned are now under investigation.

Police officers are entitled to use force when they or members of the public are under threat. And police officers have the discretionary power to decide whether the threat is immediate or serious enough to justify their using force. But that power arms the police to protect public security, not to bully others.

In other words, the police's countermeasures should be proportional to the issues they intend to solve. Obviously, the two Lanzhou police officers' violence was unwarranted and had no legal basis as there was no threat involved, either to themselves or the public.

In the first place, the police officer who kicked the man, who had already submitted himself to police control, infringed upon the man's legal rights and violated police regulations.

The two college students had the right as citizens to supervise the police law enforcement process. The policemen had no legal reason to confiscate their phones, and did so just because they feared the video would cause them further trouble.

They knew they were in the wrong. But they tried to cover it up.

Worse, the police officers then further abused their power by assaulting the students.

The officers had no justification for restricting the two students' freedom and taking them to the police station by force, where the violence inflicted on them was predictable.

Such a beating is unlikely to kill someone. However, it is an assault and such brutality by the police violates the law.

The statement of the superior public security authority in the city indicates it did not know about the case until the photos appeared online. Were it not for the pressure of public opinion, the authority would have been unlikely to act.

The question is whether the public security system's self-monitoring and self-discipline mechanisms can function well when they are needed, no other police officers intervened to stop the physical punishment meted out to the students.

That is not to deny, the police don't contribute to maintaining social stability and protecting public security. Nearly 500 police officers are killed in the line of duty every year in China. But that only further highlights the necessity of using institutional means to remove the rotten apples from the basket. Otherwise, what ends up being beaten by police batons is the rule of law.

The author is a writer with China Daily. liyang@chinadaily.com.cn

(China Daily 05/21/2016 page5)