Regicide is the killing of a reigning monarch, and the word also names the person who commits the act. The term comes from the Latin rex (king) and cida (killer). For most of legal history, regicide was not prosecuted as ordinary murder. Because the sovereign was treated as the embodiment of the state, killing a king or queen was understood as an attack on the government itself, and the law responded with its most severe category of offense: high treason.
What Regicide Means in Law
English law set the template that most European systems followed. The Treason Act 1351 made it high treason to “compass or imagine the Death of our Lord the King, or of our Lady his Queen or of their eldest Son and Heir.”1Legislation.gov.uk. Treason Act 1351, Section II The protection covered the reigning monarch, the queen consort, and the heir, so the entire royal line was shielded.
The phrase “compass or imagine” matters. It meant that planning or conspiring to kill the sovereign was itself the completed crime. A would-be regicide did not have to succeed, or even attempt the act, to be convicted of treason. Intent alone was enough. That is a sharp departure from ordinary homicide law, where prosecutors generally must prove a killing actually occurred.
Legal theorists justified this by describing the offense as a breach of allegiance. The subject owed loyalty to the sovereign as the source of their legal protection, and turning against the sovereign was turning against the social order itself. A murderer harmed an individual; a regicide, in this view, harmed the nation. That framing kept regicide out of the ordinary criminal courts and at the top of the hierarchy of crimes.
Lone Assassins and Judicial Regicide
Legal history divides regicides into two categories. The first is the lone assassin, acting from personal grievance, ideology, or political extremism, who kills a monarch outside any legal process and is prosecuted as a criminal. The more complicated category is judicial regicide, where a body claiming legal authority tries the monarch and carries out an execution.
Charles I
The leading English example is the execution of Charles I in January 1649. After the civil war between Parliamentarian and Royalist forces, Parliament set up a High Court of Justice to try the king for treason against England. Of 135 commissioners appointed to the court, 68 were present when the death sentence was pronounced, and 59 signed the execution warrant.2Wikipedia. List of Regicides of Charles I of England Those signatories did not see themselves as criminals. They believed they were holding a tyrant to legal account.
The Restoration in 1660 reversed that reading. Parliament passed the Indemnity and Oblivion Act, pardoning most people who had served under the Protectorate, but it deliberately excluded the men who had signed the king’s death warrant. Those convicted faced the statutory penalty for high treason, and several were hanged, drawn, and quartered. Others were imprisoned for life, and some escaped abroad.
Louis XVI
France followed a similar pattern in January 1793. The National Convention, acting as both legislature and court, convicted Louis XVI of conspiracy and treason against the state and sentenced him to the guillotine. Where the English warrant carried 59 signatures, the French execution rested on a vote of hundreds of elected representatives, which gave it a broader democratic character. The execution reshaped the French Revolution and alarmed every monarchy in Europe.
These cases expose a tension inside the concept. When a single person kills a king, the legal system can process the event as a crime. When the legal system itself kills the king, the question of legitimacy is harder to resolve. Participants in both the English and French regicides believed they were acting lawfully. Later governments disagreed.
How Regicide Has Been Punished
For centuries, the English punishment for high treason was designed to be agonizing and public. The convicted traitor was drawn on a hurdle to the place of execution, hanged until nearly dead, disemboweled while still alive, then beheaded and quartered. Body parts were displayed in public as a warning. That was the sentence imposed on the Charles I regicides who were caught after the Restoration.
The modern position is very different. The Crime and Disorder Act 1998 removed every reference to capital punishment in the treason statutes and replaced it with a maximum sentence of life imprisonment.3Legislation.gov.uk. Crime and Disorder Act 1998, Section 36 A conviction for treason against the Crown today carries life in prison at most. The Treason Act 1351 itself remains in force, one of the oldest statutes still on the English books.
The American Equivalent
The United States has no monarchy, and no federal crime is called “regicide.” But federal law creates a parallel framework that treats attacks on senior officials as substantially more serious than crimes against private citizens.
Killing the President, Vice President, President-elect, or the next officer in the line of presidential succession carries the same penalties as first-degree murder, including the possibility of the death penalty. An unsuccessful attempt can bring life in prison. Conspiracy to kill any of these officials also carries up to life, or the death penalty if the target dies.4Office of the Law Revision Counsel. 18 USC 1751 – Presidential and Presidential Staff Assassination, Kidnapping, and Assault
A separate statute echoes the old “compass or imagine” standard. Knowingly and willfully threatening to kill or harm the President, Vice President, or their successors is a federal crime punishable by up to five years in prison.5Office of the Law Revision Counsel. 18 USC 871 – Threats Against President and Successors to the Presidency The threshold for a threat charge is far lower than for assassination, and prosecutions are routine.
Federal law also protects foreign leaders on U.S. soil. Killing or attempting to kill a foreign head of state, prime minister, ambassador, or other internationally protected person inside U.S. jurisdiction triggers federal murder or manslaughter penalties. The statute reaches current and former heads of state, family members present in the country, and diplomats on official business.6Office of the Law Revision Counsel. 18 USC 1116 – Murder or Manslaughter of Foreign Officials, Official Guests, or Internationally Protected Persons
One feature of American treason law is a deliberate break from the English tradition. Under the old doctrine of corruption of blood, a traitor’s descendants lost the right to inherit, so entire families were punished alongside the convict. Article III of the Constitution forbids that result. Congress can set the punishment for treason, but “no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted.”7Constitution Annotated. Article III Section 3 Property can be seized during the convict’s life, but children and grandchildren keep their right to inherit.
When the Monarch Is the Defendant
For most of legal history, a sitting head of state was effectively untouchable in foreign courts. The doctrine of sovereign immunity shielded even rulers who committed grave crimes from prosecution outside their own country. The Rome Statute, which created the International Criminal Court in 2002, pushed against that principle.
Article 27 provides that the statute “shall apply equally to all persons without any distinction based on official capacity” and that being a head of state or government “shall in no case exempt a person from criminal responsibility.” It adds that immunities attached to official capacity under national or international law “shall not bar the Court from exercising its jurisdiction over such a person.”8International Criminal Court. Rome Statute of the International Criminal Court – Article 27
That inverts the traditional logic. Treason law treated the killing of a monarch as the ultimate crime because the monarch was above the law. International criminal law now contemplates putting heads of state in the dock for their own conduct. Whether the framework is enforced consistently is a separate question, but the legal architecture now exists to prosecute the very figures regicide law was built to protect.