A GLANCE AT THE news from China on Friday might suggest a political system reacting properly to high-level wrongdoing. The former boss of Chongqing, Bo Xilai, once one of China’s most powerful regional figures, was expelled from the Communist Party and, according to official news media, faces charges of corruption. Earlier, Mr. Bo’s wife was convicted and given a suspended death sentence for the murder of a British businessman. Mr. Bo is a son of one of the party’s revolutionary founders, so his punishment must have been an agonizing decision for the secretive party clique that rules China.

But does the official version of events in Chongqing match what really happened? Given China’s opaque court system and controlled media, there’s no way to know. A more useful lesson of how law is used in China is provided by a decision that came Thursday from Beijing’s No. 2 People’s Intermediate Court.

The court rejected a second and final appeal by dissident artist Ai Weiwei against a $2.4 million fine for tax evasion. In the appeal, Mr. Ai accused the tax bureau of violating laws in handling witnesses and gathering evidence in his case. The court dismissed those claims in a ruling delivered abruptly to Mr. Ai by telephone. Mr. Ai, who was incarcerated for 81 days last year in a crackdown on dissidents, has long maintained the tax fine is retaliation for his outspoken criticism of China’s abuse of human rights. The authorities have retained Mr. Ai’s passport, preventing him from attending exhibitions of his work abroad, but he has refused to be silenced.

“What surprises me is that this society, which is developing at such a rapid rate today, still has the most barbaric and backward legal system,” he said. “I think it’s a bad omen.”

China possesses courts, laws and judges. But as Mr. Ai’s case attests, China still is not governed by rule of law, the simple but unshakable principle that no one — not the party, not the Politburo — is above the law.

China’s Communist Party bosses see the law as a tool of control, a method to intimidate those who challenge their policies or their monopoly on power. Chen Guangcheng, a blind lawyer who left China this year after being repeatedly imprisoned and persecuted, has eloquently stated that the problem is not an absence of laws but rather the way laws are arbitrarily enforced. A larger point is that rule of law is the best method for regulating competition among different groups in society, for settling disputes and serving as a check against abuse of power. It is an essential pillar of democracy, a concept that fills China’s leaders with trepidation.

In the case of the ousted Mr. Bo, it seems the party wanted to dispose of the embarrassing scandal before the Nov. 8 opening of the 18th Party Congress, at which the next generation of leaders will be anointed. But the high-profile expulsion of Mr. Bo only reinforces a sense that it is the party, and not the law, that reigns supreme.