The Cardassian Union (also referred to as the Cardassian Empire and colloquially often simply called Cardassia) is the official governing body of the Cardassian people. The capital world is Cardassia Prime.
The Cardassian Union was formed under a treaty that established a power-sharing agreement between the Cardassian Central Command and the Obsidian Order. Friction has always existed between the two organizations as the Central Command worked to expand the reaches of the Union and the Obsidian Order worked to suppress it. The civilian Detapa Council was established to serve as the chief governing body between the two branches, however, in practice, the Council was virtually powerless. (DS9: "Defiant")
In late-2371 or early-2372, following the fall of the Obsidian Order at the Battle of the Omarion Nebula, the Detapa Council and the Cardassian dissident movement overthrew the Central Command, establishing control over the government. (DS9: "The Way of the Warrior")
In 2373, Gul Dukat secretly negotiated with the Dominion for the Cardassian Union to become its newest members. The Detapa Council was overthrown and Gul Dukat established himself as ruler of the Cardassian Union. (DS9: "By Inferno's Light") This arrangement was later revealed to be inaccurate as Dukat (and his successors Legate Damar and Legate Broca) were actually subservient to the Vorta and the Founders.
The Cardassian Guard is lead by the Central Command and the Cardassian forces are divided into several orders. The Obsidian Order, the intelligence agency of the Union, is sometimes referred to as part of the structure of the Cardassian military orders. (See also: Cardassian ranks)
The highest court of justice in the Cardassian Union is the Cardassian Supreme Tribunal. The Cardassian Articles of Jurisprudence provide the laws governing treatment and rights of prisoners in the Cardassian justice system. (DS9: "Tribunal")
During the 24th century, the Cardassians maintained trade alliances with the Valerians and Klaestrons. They also were known to use the Xepolites and Lissepians as trade intermeditaries in arrangements that may otherwise be considered illegal outside of the Union. (DS9: "Dax", "Dramatis Personae", "The Maquis, Part II")
Many of the primary worlds in the Cardassian Union lacked an abundance of natural resources. For this reason, the Union relied heavily on strip mining resources from neighboring planets which were not part of other Alpha Quadrant powers, such as Bajor. As opposed to making trade alliances with them, the Cardassian Central Command would often instill occupations on worlds and use the populations as forced laborers. (TNG: "Ensign Ro"; DS9: "Emissary", "Duet")
See: Occupation of Bajor
The lek is the common form of currency within the Union. (VOY: "Caretaker")