The CoDominium (CD) was a supranational alliance of the United States of America and the Union of Soviet Socialist Republics. This alliance eventually became a de facto planetary government on Earth, and later, an interstellar empire. Despite this, no other nations on Earth are given representation or membership. Other major powers become mere client states. It was governed by a "Grand Senate", which is composed of Senators chosen from the two superpowers. A CoDominium Council existed and appeared to function as a judicial branch. It should be noted that the CD did not unify the United States and the USSR, who retained their separate identities and mutual distrust. The CD was only created for the shared benefit of the two member states. It did not govern either nation, and each state was allowed to retain their government structures, nationalities, militaries, and to run their own internal affairs.

Government departments

Bureau of Corrections (BuCorrect): Agency for criminal corrections of the justice system.
Bureau of Personnel (BuPers): Responsible for the staff in all government departments.
Bureau of Relocation (BuReloc): Responsible for off-planet transportation of colonists and deportees, voluntary or otherwise.
Bureau of Technology: Restricts what studies people can learn.
CD Intelligence Services (BuInt): Suppresses research and development.
Colonial Bureau: Helps run colony worlds by providing planetary governors, law enforcement, and other specialists.
CoDominium Space Navy and Marines: The Marines are divided into 3 branches: Fleet, Garrison and Line. (The Fleet): Armed forces of the CD, headed by a Grand Admiral. Edicts of the Grand Senate are enforced by the CD's armed forces. Other functions is keeping the peace on Earth and other worlds.
Intercontinental Bureau of Investigations (IBI): Presumably the CD equivalent of the FBI.

Sources: A Spaceship for the King, West of Honor, The Mercenary, Prince of Mercenaries, Falkenberg's Legion, Go Tell the Spartans, Prince of Sparta, The Prince