The Systems Commonwealth, an interplanetary, interstellar government within the Pocket Universe containing thousands of worlds, contains most of the planets and solar systems that broke away from the New Shi'ar Imperium during the Era of Anti-Imperial Rebellions (Years 6500 to 7000 of the New Shi'ar Calendar). 

The Commonwealth was actually formed in Year 6904 of the New Shi'ar Calendar.  It's relations with the New Shi'ar Imperium has varied over the centuries, though only in the first 50 years or so of the Commonwealth have the Imperium and the Commonwealth have been in full-scale war. 

More often, the Systems Commonwealth has been at war with the Cylons, Kurgan Caliphate, United Pirate Clans, the Sontarans, and certain factions of Orks

The majority of Commonwealth citizens are Humans, although non-human races, including a surprisingly large number of Shi'ar, live within the Commonwealth as well.

The Commonwealth government includes the Systems Commonwealth Parliament appointed by local planetary governments, the Senate of the Commonwealth elected by the Parliament (with senators serving a 25-year term of office), a Prime Minister and a Council of Ministers responsible to the Parliament (can be voted out of office by a Parliament majority), and a First Citizen elected by the Senate for a 25-year term of office and serving as a symbolic head of state. 

Politics in Parliament and the Senate are based upon a two-party system:  the Alliance Party (which favors a close alliance between the Systems Commonwealth and the New Shi'ar Imperium) and the Anti-Imperial Party (composed of Commonwealth politicians hostile to the New Shi'ar Imperium).

The police forces of the Systems Commonwealth are the Judicial Forces and the Commonwealth military forces are the Unified Planetary Forces. Orks hired by the Commonwealth as mercenaries are generally placed under the command of the Judicial Forces or the Unified Planetary Forces.

Religion within the Commonwealth is mostly based upon the Church of the True God (both the official Church headquartered on Chandilar and local splinter sects are active on Commonwealth worlds) and to a lesser degree on the Pantheon of the Old Gods.  The Commonwealth government itself is officially secular.

In the Pocket Universe in Year 12,600, the Systems Commonwealth had been absorbed into the United Worlds.