if the government simply band smoking, it will create a explicit discrimination to the smoker and damage the concept of "free market", the freedom contravene to "Basic Law" where it enshrines a legal document the important concepts of “one country, two systems”, “a high degree of autonomy” and “Hong Kong People ruling Hong Kong”. It also prescribes (規定) the various systems to be practiced in the HKSAR.
when government just band the smoker not smoking in certain areas. They have the choice, even though the places are limited.