Does the power to inquire extend to officials in the executive branch?
Yes. The power of inquiry is broad enough to cover officials of the executive branch. The power of inquiry is co-extensive with the power to legislate. The matters which may be a proper subject of legislation and those which may be a proper subject of investigation are one. It follows that the operation of government, being a legitimate subject for legislation, is a proper subject for investigation. Since Congress has authority to inquire into the operations of the executive branch, it would be incongruous to hold that the power of inquiry does not extend to executive officials who are the most familiar with and informed on executive operations. Are there limitations to this power? If yes, what are these limitations? Yes. As now contained in the 1987 Constitution (Section 21, Article VI), the power of Congress to investigate is circumscribed by three limitations, namely: (a) it must be in aid of its legislative functions, (b) it must be conducted in accordance with duly published rules
