Royal commission

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, 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.
The commission is created by the head of state (the sovereign, or their representative in the form of a governor-general or governor) on the advice of the government and formally appointed by letters patent. In practice—unlike lesser forms of inquiry—once a commission has started the government cannot stop it. Consequently, governments are usually very careful about framing the terms of reference and generally include in them a date by which the commission must finish.
Royal commissions are called to look into matters of great importance and usually controversy. These can be matters such as government structure, the treatment of minorities, events of considerable public concern or economic questions. Many royal commissions last many years and, often, a different government is left to respond to the findings.
Notable royal commissions.
Australia.
Royal commissions (sometimes called commissions of inquiry) have been held in Australia at a federal level since 1902. Royal commissions appointed by the Governor-General operate under the Royal Commissions Act 1902 passed by the Parliament of Australia in 1902. 
Royal Commissions are the highest form of inquiry on matters of public importance. A Royal Commission is formally established by the Governor-General on behalf of the Crown and on the advice of Government ministers. The government decides the terms of reference, provides the funding and appoints the commissioners, who are selected on the basis of their independence and qualifications. They are never serving politicians.
Royal commissions are usually chaired by one or more notable figures. Because of their quasi-judicial powers the commissioners are often retired or serving judges. They usually involve research into an issue, consultations with experts both within and outside government and public consultations as well. The warrant may grant immense investigatory powers, including summoning witnesses under oath, offering of indemnities, seizing of documents and other evidence (sometimes including those normally protected, such as classified information), holding hearings "in camera" if necessary and—in a few cases—compelling all government officials to aid in the execution of the Commission. The results of Royal Commissions are published in reports, often massive, of findings containing policy recommendations. (Due to the verbose nature of the titles of these formal documents – for example, the Royal commission into whether there has been corrupt or criminal conduct by any Western Australian Police Officer – they are commonly known by the name of the commission's chair.) While these reports are often quite influential, with the government enacting some or all recommendations into law, the work of some commissions have been almost completely ignored by the government. In other cases, where the commissioner has departed from the Warranted terms, the commission has been dissolved by a superior court.