Government and politics

The United Kingdom is a constitutional monarchy: Queen Elizabeth II is head of state of the UK as well as of fifteen other Commonwealth countries, putting the UK in a personal union with those other states. The Crown has sovereignty over the Crown Dependencies of the Isle of Man and the Bailiwicks of Jersey and Guernsey, which are not part of the United Kingdom though the UK government manages their foreign affairs and defence and the UK Parliament has the authority to legislate on their behalf.

Since the United Kingdom is one of the three countries in the world today that does not have a codified constitution, the Constitution of the United Kingdom consists mostly of written sources, including statutes, judge made case law, and international treaties. As there is no technical difference between ordinary statutes and "constitutional law," the UK Parliament can perform "constitutional reform" simply by passing Acts of Parliament and thus has the power to change or abolish almost any written or unwritten element of the constitution. However, no Parliament can pass laws that future Parliaments cannot change.

The UK has a parliamentary government based on the Westminster system that has been emulated around the world — a legacy of the British Empire. The Parliament of the United Kingdom that meets in the Palace of Westminster has two houses: an elected House of Commons and an appointed House of Lords, and any Bill passed requires Royal Assent to become law. It is the ultimate legislative authority in the United Kingdom since the devolved parliament in Scotland and devolved assemblies in Northern Ireland, and Wales are not sovereign bodies and could be abolished by the UK parliament despite being established following public approval as expressed in referenda.