When Chinese President Xi Jinping pledged to "safeguard the rights of people in line with law" in his New Year address, Xu Liangju was in a cell for seeking government action over the killing of her teenage son.

On a winter morning, the 45-year-old was muscled into a van, taken to a police station, driven seven hours to her home province of Henan and sentenced by police to 10 days' detention.

Her crime? "Illegally petitioning outside Zhongnanhai", the heavily guarded central leadership compound next to Beijing's Forbidden City.

China's Communist Party-controlled legislature, the National People's Congress (NPC), gathers in the capital this week with the "rule of law" high on the agenda.

It is one of Xi Jinping's "Four Comprehensives" in a newly proclaimed political theory, but the concept has a different meaning in China than elsewhere.

Last week the country's supreme court denounced "judicial independence" and "separation of powers", calling on judges to "resolutely resist the influence of the West's erroneous thought and mistaken viewpoints".

Analysts say the "rule of law" is seen as a way for China's rulers to exercise authority, rather than be subordinate to it themselves.

Not even Party cadres are safe. The ruling organisation's feared internal Central Commission for Discipline and Inspection (CCDI) operates its own justice system known as "shuanggui," beyond external legal control.

Its investigators have essentially free rein over suspects and there is no right to legal counsel.

Xi's two-year-old anti-corruption drive -- likely to be trumpeted as a triumph at the NPC -- has seen thousands of officials disappear into CCDI custody.

Typically, several months later they will be ruled to have violated party rules and handed to judicial authorities for prosecution, with their guilt already pronounced.

- Follow the rules -

China's former premier, Wen Jiabao, once said: "The gate to Zhongnanhai is open to the people". But Xu is among the millions of "petitioners" who have found the doors of power closed firmly in their faces.

Every year they present their complaints to the Bureau for Letters and Calls, a government agency with offices across the country, under a system established during imperial times.

Her eldest son, Zhang Pengfei, was 15 in 2007 when he was killed in a confrontation with schoolmates after a classroom argument.

The boys were convicted of "injury resulting in death" and sentenced to up to 15 years in prison, but Xu says they should have been charged with intentional homicide and ordered to pay her compensation. Years trying to change the decision have proved fruitless.

"If Xi wants to rule the country according to the law, why can't the government resolve a small and simple case like mine?" she told AFP in a windowless concrete room she shares with her five-year-old second son on Beijing's outskirts.

"I was hopeful when Xi became president, optimistic that the government would finally start following the rules. But for me, it's become worse."

- 'Just a phrase' -

A high-level meeting in November proclaimed the Communist Party's commitment to the "rule of law with Chinese characteristics".

In a commentary last week the official Xinhua news agency said: "Catapulting a nation long entrenched in a tradition of rule by men into a law-abiding society is... a revolution that will have a far-reaching impact."

It added that measures being taken "showcase that China's determination to build a law-abiding society and government is not empty words, dashing Western media reports alleging that China's efforts to pursue the rule of law are futile".

But the authorities stress that the principle of the Party's leadership is vital, while under Xi the promises of legal reform have been coupled with a sweeping crackdown on dissent.

Experts say the repeated rhetoric has yet to be accompanied by practical change.

"In the past year or two, there hasn't been any progress on China's rule of law and actually it's gone backwards," said Zhang Xuezhong, a lawyer who has represented reform advocates.

"Every leader, from (former presidents) Jiang Zemin to Hu Jintao to Xi Jinping, all talk about rule of law," said Zhang, a former professor at East China University of Political Science and Law. "But for them it's just a phrase in a speech."

Instead of helping to shine a light on local corruption, petitioners are usually met with police harassment, stints in "re-education through labour" camps -- whose abolition was announced in 2013 -- and beatings.

Cases are left unresolved for years or decades, usually for ever.

In 2013, officials resolved less than 0.1 percent of the nearly two million new complaints at all levels of government, according to a white paper published by the State Council, China's cabinet.

But after years of petitioning, time in detention, their life savings exhausted and suffering a sometimes severe psychological toll, many still doggedly pursue their causes, with no other life left to return to.

"Being emotional won't bring him back and it won't help my case," Xu said. "I don't even cry anymore, not about my dead son, or the injustice."