With the exception of the power to commission research, a sub-committee has all the powers, privileges and immunities of a Joint Investigatory Committee. It is usual for select committees appointed by resolution of the Houses to hold office for the duration of the session in which they were appointed. Any committee which has not completed its task on the prorogation of a session needs to be reappointed in the following session if it is to continue its inquiry. The Joint Investigatory Committees differ from select committees in that they hold office for the duration of a Parliament and therefore cease to exist only upon the expiry of the Assembly by effluxion of time or upon the dissolution of either House of the Parliament. Where a Joint Investigatory Committee has taken evidence in relation to a particular inquiry but ceases to exist before reporting on the matter to the Parliament, section 4S of the Parliamentary Committees Act 1968 provides for that evidence to be considered by any subsequent committee.
All parliamentary committees have the power to call for persons, papers and records.
This power is derived from section 19 of the Constitution Act 1975 which provides that the Council and the Assembly shall hold, enjoy and exercise such privileges, immunities and powers possessed by the House of Commons in 1855. This section also confers on each House the power to legislate for or with respect to the privileges, immunities and powers enjoyed and exercised by both Houses and by the committees and the members thereof respectively. The Act also empowers the Council and the Assembly and their committees to administer an oath or affirmation to a witness, and provides that no action for defamation shall be maintainable for anything said in evidence. It should be noted that the Parliamentary Committees Act 1968 relates only to Joint Investigatory Committees and does not automatically apply to select or joint select Committees. Its application to select committees would need to be invoked by the resolution or Act establishing the committee.