AMID all the publicity surrounding the growing momentum towards the setting up of a ''new kitchen'' at the National People's Congress (NPC) in Beijing last week, the real threat to Hongkong's future passed almost unnoticed. It is a threat that is one of the most ominous warnings yet of how easily China's promises of ''one country two systems'' and ''Hongkong people ruling Hongkong'' may turn out to be scarcely worth the paper they are printed on. Of how there may be little point in the present battle over electoral arrangements, since the Legislative Council could easily be stripped of its powers by the rubber-stamp NPC - a body that was last week busy demonstrating how it endorses everything putto it by the Communist Party leadership. It is a threat that has little to do with the topic that has so far attracted the most attention - the dismantling of the through-train and the holding of fresh elections in 1997, something now taken increasingly for granted. For that prospect, unpleasant though it may be, has been on the cards ever since it was written into the Basic Law that a Beijing-appointed committee will decide which legislators survive the transition. Instead it came in comments by one of China's top legal experts on the Basic Law, former drafter Mr Wu Jianfan, who said the NPC should start the process of establishing a ''new kitchen'' over the Court of Final Appeal, because the British and Hongkong governments had failed to implement the controversial 4+1 agreement reached by the Joint Liaison Group. That prospect is bad enough in itself. Confidence in Hongkong's maintenance of a fair legal system, something crucial to the territory's future prosperity, would be severely shaken by the setting-up of its highest court by a parliament dominated by communists who know little about the common law system. YET the real threat comes from the justification used for the NPC legislating to establish the new court, and the dangerous precedent that this sets for some of Hongkong's most fundamental freedoms. Mr Wu, a senior figure at China's prestigious Academy of Social Sciences and Beijing's de-facto spokesman on the issue, did not go into details last week. But he has made the position all too plain in previous articles in the left-wing press, claiming that when Article 83 of the Basic Law states the workings of Hongkong's courts shall be ''prescribed by law'', that can refer to a mainland law passed by theNPC rather than a Hongkong law passed by Legco. The alarming thing about that extreme interpretation - which few, if any, foresaw at the time of the drafting of the Basic Law - is that the same phrase crops up throughout Hongkong's future mini-constitution, as it sets out the rights supposed to exist after 1997. That means China's claim that the NPC can pass a law to set up the Court of Final Appeal also means that the rubber-stamp parliament has the right to pretty much do what it wants to curb the liberties of Hongkong people. For Article 39 states ''the rights and freedoms enjoyed by Hongkong residents shall not be restricted unless as prescribed by law'', leaving the door wide open for the communist-dominated legislature to curtail local liberties. Other parts of the Basic Law, interpreted in the same extreme way, imply that the NPC also has the right to pass laws about the local financial and monetary systems, devaluing the Hongkong dollar for instance, or restricting the right of people to enter and leave the territory. Mr Wu, when contacted by the Sunday Morning Post in Beijing last week, was reluctant to discuss the full consequences of his argument. ''I don't see why the NPC shouldn't have these powers . . . after all, the whole Basic Law was passed by the NPC,'' he said. But he was evasive on whether this meant China's parliament also had the right to curb Hongkong's freedoms, saying only that some references to laws in the mini-constitution meant mainland NPC laws, although most meant Hongkong Legco laws. However the head of a pro-China think-tank in Hongkong was more explicit. ''There's nothing anywhere barring the NPC from making any laws for Hongkong,'' said One Country Two Systems Economic Research Institute executive director Mr Shiu Sin-por. THE meaning is clear enough: China can pick and choose whether it wants to pass harsh mainland laws through its rubber-stamp parliament, or whether it wants to preserve a fig-leaf of autonomy, by leaving some for the post-1997 Legco to legislate over. In other words, it may not matter much whether councillors are elected through the quasi-democratic Patten package or some more conservative model since, either way, they will have few real powers. And it is perhaps the clearest example yet of how Beijing can interpret and re-interpret the Basic Law to suit its purpose. Indeed, China could yet twist the mini-constitution back to a less extreme meaning, by citing some ambiguous limitations on the NPC's power set out in Article 18, if Mr Wu's interpretation causes too much alarm. Yet, either way, it is a timely reminder that the Basic Law and the Joint Declaration are ''just pieces of paper'' - as Lady Dunn once said. So perhaps the influential mainland drafter has done Hongkong a service by demonstrating how there is no point in placing too much faith in a document China has now shown it can re-interpret at will.