Melamine is back. Tonnes of milk powder laced with the toxic industrial chemical were found during quality control testing in Gansu and Qinghai provinces. The scandal two years ago that killed six children and made 300,000 ill damaged the nation's image and the trust of Chinese in their dairy industry, but the reforms that were put in place and the stiff sentences handed down have not prevented its return. Surely, one might ask, are not two executions, 21 arrests and jail terms for dairy officials and workers enough of a deterrent? Affluent mainland parents who buy their milk powder from Hong Kong clearly do not think so, and this seizure vindicates their cautiousness. At heart, the issue for those parents is not deterrence; it is confidence that there is a structure to effectively enforce laws and regulations so that any and all lawbreakers are held to account. It is not clear where the 76 tonnes of melamine came from - it may have been hidden from officials who destroyed stocks, or been newly produced. Still, the manner in which the melamine was found shows the changed attitude to two years ago. In contrast to the near-silence of officials then in the lead-up to the Beijing Olympic Games, there are inspections and tests and police are willing to act. That is a big improvement; and an important step forward in building greater confidence that other similar cases will be investigated and brought to light. Sadly, corruption and greed will always provide a motive for companies - or inspectors - to focus on turning a quick buck. No jurisdiction is immune, and unsafe goods can be found in every country on earth. The mainland is no exception. Still, this case provides a timely reminder of the importance of a sound legal system, where all people are accountable and treated equally in the eyes of the law - and more importantly, justice is seen to be done. Punishment, harsh or otherwise, can help serve as a deterrent, but far more critical is the expectation among citizens that the law was enforced in a fair and even-handed manner. The mainland's legal system continues to develop - Beijing has launched programmes to educate judges about overseas legal systems, for example, and there has been increased spending on court buildings and services. Those are all positive steps; a key test will be when mainland parents who have a choice prefer to buy their milk powder locally.