Constitutional theory in law refers to the study and analysis of the principles, concepts, and structures underpinning a country's constitution. It examines the fundamental rules and principles that govern the relationships between various arms of government and the relationship between the state and its citizens. This helps to create a framework for understanding and interpreting the constitution, as well as shaping legal decision-making and policy formation. In the UK context, constitutional theory explores the unwritten constitution and its development through historical documents, statutes, legal conventions and key court decisions.