A rigid constitution is a feature of a federal system. A federal system is a form of government where power is divided between a central authority and constituent political units, such as states or provinces. A rigid constitution is a constitution that cannot be easily amended or changed. In a federal system, the constitution is usually designed to be difficult to amend, so that it provides a stable framework for the distribution of powers between the central government and the constituent political units. This helps to prevent one level of government from becoming too powerful, and ensures that power is shared between different levels of government.