Luckily for Chan Yuk-to, the Hong Kong resident expelled from the mainland for being a Falun Gong follower, he had a mother ready to fight for his freedom. Lau Yuk-ling completed a three-day marathon around the SAR collecting signatures for a petition to secure her son's release. Her bold, high-profile action was exactly what was needed after Beijing failed to notify the family of his detention. Mr Chan was quietly sent back across the border on Saturday. For his 'crime' of playing host to two fellow Falun Gong practitioners in his Beijing flat, he has been banned from returning to the mainland for five years. It is a severe punishment, as the ban effectively cost him his job. But the 35-year-old technician is better off than detainees who have no family to raise the alarm. Two SAR residents are caught in that trap today. Chu O-ming has been in detention since he was arrested for trying to sue President Jiang Zemin for his crackdown on the Falun Gong movement. Single mother Huan Yueshao is held for debts allegedly run up by her boyfriend, but her plight was unknown until a sister on the mainland filed a request for assistance. The failure of mainland public security officials to notify the SAR Government of these arrests is a cause for concern, but it is not the only one. The rule that the Hong Kong Security Bureau cannot act for someone caught across the border unless asked to do so by a relative is another loophole. Also disturbing is the way the justice system on the mainland is being violated. The Chinese Criminal Procedure Law requires a detainee's family to be notified of a detention within 24 hours. That has not been done in any of these cases involving SAR residents. If Mr Chan's version of events is accurate, his legal rights were further violated when his home was searched without a warrant being produced beforehand. The SAR Government is justifiably cautious about seeming to interfere in mainland affairs. But it cannot be called meddling to draw attention to malpractice by police or security officials if it affects the welfare of Hong Kong citizens. Authorities here have a duty under Article 4 of the Basic Law to safeguard the rights and freedoms of SAR residents, and the mainland is under precisely the same obligation to honour that provision. This involves both sides ensuring that correct legal procedures are followed when SAR residents fall foul of mainland law, regardless of guilt or innocence. More urgently, when a legal oversight in the notification system results in lone residents being abandoned to their fate, quick action is needed to set matters right. In an equitable society, there cannot be one law for those with relatives, and none for those without.