President Park Geun-hye said Thursday the government will deal sternly with vested interests taking illegal collective action to hold on to their rights, an apparent reference to doctors threatening another walkout in protest of healthcare policies. "It is difficult to realize economic innovation while ignoring illegal collective action aimed at protecting vested rights," Park said during the graduation ceremony of the Korea National Police University. "It is difficult to open an era of national unity and unification while overlooking illegal acts and disorder shaking national discipline and social safety."    The remark was apparently in reference to doctors threatening to go on strike again later this month after their one-day walkout earlier this week to protest the government's plan to allow telemedicine services and profit-oriented hospitals.