The separation of powers principle deeply heritaged in the US constitutionalism affected and continues to influence the law and public policy in the nation. The tripartite scheme of government was quarreled over the history how we have to perceive any best adequate interaction among the Congress, Executive and Judiciary. The Constitution itself merely quibbles on this point, and the Supreme Court justices, in some cases, would not be done as a clear cut for the scope of constitutional power conferred on (...) each branch. As the stare decisis is a rule in the common law countries, it is less prospective to anticipate that a quantum leap can be made for the new paradigm of constitutional government in the US. In this challenge, the paper deals with the sensitive area of three powers involving the issue of presidential privilege and immunity, justiceability and standing, as well as judicial control of public agencies. In the course of discussion, several landmark cases were illustrated to make a point for the angulated controversies, typically involving the pressing pubic issues and officers of absolute or qualified immunity. Given the diverse structure of government, the US model had been followed by many new born republics in 20th centuries. The author would wish that the paper provides a comparative lesson for the circle of those countries. (shrink)