The United Kingdom is a unitary state under a constitutional monarchy. Queen Elizabeth II is the monarch and head of state of the UK, as well as 15 other independent countries. These 16 countries are sometimes referred to as "Commonwealth realms". The monarch has "the right to be consulted, the right to encourage, and the right to warn". The Constitution of the United Kingdom is uncodified and consists mostly of a collection of disparate written sources, including statutes, judge-made case law and international treaties, together with constitutional conventions. The UK Parliament can perform "constitutional reform" simply by passing Acts of Parliament, and thus has the political power to change or abolish almost any written or unwritten element of the constitution. No Parliament can pass laws that future Parliaments cannot change.