A royal commission is a major ad-hoc formal public inquiry into a defined issue in some monarchies. They have been held in the United Kingdom, Australia, Canada, New Zealand, Norway, Malaysia, Mauritius and Saudi Arabia. A royal commission is similar in function to a commission of inquiry (or, less commonly, enquiry) found in other countries such as Ireland, South Africa, and regions such as Hong Kong. It has considerable powers, generally greater even than those of a judge but restricted to the terms of reference of the commission. These powers include subpoenaing witnesses, taking evidence under oath and requesting documents.