Colonial Administration Authority

The Colonial Administration was an organization under the ultimate control of the Unified Earth Government. The CA was an administration that likely helped the UEG govern the various colony worlds of humanity and kept extensive files on every colony, world, and city under its care. These files contained everything from topographic maps to the information on the materials the city sewer system was built from. The CA provided this information to ONI special weapons teams upon request. It could be very helpful when defending colonies from Covenant attack.

Over the course of the Human-Covenant War, the UNSC had largely taken over many of the responsibilities of other branches of the government. The CA was described as "a little more resistant to the idea than the UEG and has subsequently been stripped of most of its power." It is therefore likely that it no longer exists in any functional capacity by 2552.

Structure
The Colonial Authority could be the colonial arm of the United Nations, responsible for the administration of the UNSC's colonies throughout the known human-colonized galaxy.

Though the pre-release and valid announcement Halo timeline refers to it as the Colonial Administration Authority, in Halo: Contact Harvest, the organization is referred and known as just the Colonial Authority.