Mainland mothers giving birth in Hong Kong is a problem that warrants serious attention. Thanks to the liberal regime set out in the Basic Law, non-local Chinese born in the city are also eligible for permanent residency. The eligibility was upheld in a ruling by the city's top court in 2001. Since then an estimated 170,000 babies have become eligible, raising fears of a strain on public services and resources if they choose to settle here. The question of how to curb the influx has been put under the public spotlight again recently. When asked by the media during a conference in Guangzhou, Secretary for Justice Rimsky Yuen Kwok-keung said a solution would be ready in about three months. A top British lawyer, Yuen said, had been asked to give advice. We do not know what's on the government's mind at this stage. The remarks have, nonetheless, fuelled speculation that the issue will be settled in court. This includes the disturbing option of asking the city's top court to "rectify" its right of abode ruling handed down more than a decade ago. There are good reasons why this step is best avoided. The Court of Final Appeal is vested with the final adjudication power over the city's law. Back then, the court's decision to give permanent residency to those born to non-local Chinese parents was criticised for not following the interpretation by the Standing Committee of the National People's Congress on right of abode. But the government decided to live with the judgment. It would be very odd if a challenge was made 11 years later. The move will render judicial decision unreliable and undermine the rule of law. With proper planning and control, the new births can be a long-term solution to our problem of low fertility and an ageing population. The government has already imposed a zero birth quota next year and stepped up enforcement against those who give birth without bookings. Hopefully, the measures can keep the numbers to a level we can comfortably cope with.