Hong Kong has invited a Queen's Counsel to advise on how to reverse a law that automatically grants right of abode to all babies born to mainland parents in the city.
An expert on the Basic Law said the move was a strong sign the government intended to resolve the matter in the courts.
A few months ago, Secretary for Justice Rimsky Yuen Kwok-keung said seeking a reinterpretation of the relevant Basic Law clauses was not "an appropriate solution".
Yesterday, Yuen said the government had made "positive" progress in its study of the issue and promised it would be completed in "slightly longer than three months".
He did not reveal any solutions the government might have put up to the British barrister.
"Our office has studied all proposed solutions available," Yuen said in Guangzhou. "We can say that we have discussed the issues with relevant local and international legal experts.
"Our research direction has reached a stage of preliminary evaluation. We are now seeking further advice over certain aspects with a British-based veteran QC. For now we cannot reveal actual measures, but the details will be released to the public in the future."
Alan Hoo SC, chairman of the Basic Law Institute, said: "It seems the direction of the government is quite clear, that it wants legal assistance to push its case in court."
Hoo said enlisting the help of a top legal expert would increase the government's chances of persuading the top court to reach a judgment in line with a 1999 interpretation - a child born in Hong Kong would be entitled to right of abode only if at least one parent was a permanent resident at the time of birth.
He said the move would help the Court of Final Appeal "rectify" its 2001 ruling - which conferred automatic residency on babies born to mainland parents in the city.
Since that ruling, an estimated 170,000 such babies have been born in the city, prompting fears of strains on services.