Prerogative writ in the context of "Habeas corpus"

In common law, a writ is a formal written order issued by a body with administrative or judicial jurisdiction; in modern usage, this body is generally a court. Warrants, prerogative writs, subpoenas, and certiorari are common types of writs, but many forms exist and have existed.

In its earliest form, a writ was simply a written order made by the English monarch to a specified person to undertake a specified action; for example, in the feudal era, a military summons by the king to one of his tenants-in-chief to appear dressed for battle with retinue at a specific place and time. An early usage survives in the United Kingdom, Canada, Australia, and some other Commonwealth countries in a writ of election, which is a written order issued on behalf of the monarch (in Canada, by the Governor General and, in Australia, by the Governor-General for elections for the House of Representatives, or state governors for state elections) to local officials to hold a general election. Writs were used by the medieval English kings to summon people to Parliament (then consisting primarily of the House of Lords) whose advice was considered valuable or who were particularly influential, and who were thereby deemed to have been created "barons by writ".

In law, certiorari is a court process to seek judicial review of a decision of a lower court or government agency. Certiorari comes from the name of a prerogative writ in England, issued by a superior court to direct that the record of the lower court be sent to the superior court for review.

Derived from the English common law, certiorari is prevalent in countries using, or influenced by, the common law. It has evolved in the legal system of each nation, as court decisions and statutory amendments are made. In modern law, certiorari is recognized in many jurisdictions, including England and Wales (now called a "quashing order"), Canada, India, Ireland, the Philippines and the United States. With the expansion of administrative law in the 19th and 20th centuries, the writ of certiorari has gained broader use in many countries, to review the decisions of administrative bodies as well as lower courts.

A court of equity, also known as an equity court or chancery court, is a court authorized to apply principles of equity rather than principles of law to cases brought before it. These courts originated from petitions to the Lord Chancellor of England and primarily heard claims for relief other than damages, such as specific performance and extraordinary writs. Over time, most equity courts merged with courts of law, and the adoption of various Acts granted courts combined jurisdiction to administer common law and equity concurrently. Courts of equity are now recognized for complementing the common law by addressing its shortcomings and promoting justice.

In the early years of the United States, some states followed the English tradition of maintaining separate courts for law and equity. Others combined both types of jurisdiction in their courts, as the US Congress did for federal courts. United States bankruptcy courts serve as an example of a US federal court that operates as a court of equity. A few common law jurisdictions, such as the U.S. states of Delaware, Mississippi, New Jersey, South Carolina, and Tennessee, continue to preserve the distinctions between law and equity as well as between courts of law and courts of equity. In New Jersey, this distinction is upheld between the civil and general equity divisions of the New Jersey Superior Court.