A confederation is a political union of sovereign states united for the purpose of common action. It is usually created by a treaty and is established to deal with critical issues such as defense, foreign relations, internal trade, or currency, with the central government required to provide support for all its members. In a confederation, each state is independent and has its own authority and autonomy, but they come together for some sort of shared government. The central government is usually weak and tries not to interfere in the states' governments. Confederations are voluntary associations of independent states that agree to certain limitations on their freedom of action and establish some joint machinery of consultation or deliberation. They usually fail to provide for an effective executive authority and lack viable central governments; their member states typically retain their separate military establishments and separate diplomatic representation, and members are generally accorded equal status with an acknowledged right of secession from the confederation