In 2016 some pro-independence advocates in Hong Kong attempted to enter into the Legislative Council to promote their causes. Their political endeavors were thwarted by the legal means sought by the authorities. Six members-elect of the LegCo were disqualified by the courts for invalidly taking the oath. Similar controversies also played out in Taiwan as early as 1984 when some Tangwai members neglected to take their oath. The oath-taking controversies in the two regions both revolve around the political legitimacy of the existing constitutional framework. This paper will compare the oath-taking disputes and different courts‘ rulings regarding the disputes and attitudes of the relevant shareholders towards the controversial issue in the two regions. With a reference to the abstentionism tactic used by Sinn Fein members in the UK, it will highlight the uniqueness of the dilemma marked by the conflict between democratic legitimacy and the law in societies under authoritarianism.