Parliaments in many countries possess the power to conduct investigations which include compelling the attendance of witnesses before it. The limit of such power varies from jurisdiction to jurisdiction and must be determined having regard to the unique features of the relevant parliamentary system. Given that Hong Kong was previously a British colony, its parliamentary system has been influenced by the United Kingdom’s Westminster system. In addition, Hong Kong has adopted a ‘separation of powers’ governmental model and, to this extent, its governmental system resembles that of the United States of America. At the same time, the government of the Hong Kong Special Administrative Region is executive-led and operates under the principle of ‘One Country, Two Systems’. Within this context and by reference to both foreign experience and the peculiarities of the local system, this paper seeks to establish the boundaries of the investigative powers of Hong Kong’s Legislative Council through an examination of (i) the conferral of parliamentary investigative powers; (ii) the ancillary nature of parliamentary investigative powers; (iii) the impact of the principle of deference; and (iv) the role of the courts in adjudicating challenges to investigative powers.