The Oasis Government is the dominant authority within the Great Kanto Desert that had arisen presumably thousands of years after an event known as the Dark Ages in the area that had once been Japan before the event occured. It is assumed that the government had been split into several different parts each one having control over a directional region such as East, West, North and South as mentioned in the anime and manga, these may also just be outposts for those regions of the Desert to maintain order and providing the bare minimum for the citizens. It was later revealed that the Oasis Government operates out of a massive subterranean structure to the point that they only use half of the space and by the time of Episode 19 the remaining half has yet to be explored.
Oasis Government building
The Government building is found to be a structure that had been around since the Dark Ages to defend against an unknown threat that was plaguing humanity at the time. The structure itself is closed with massive white walls keeping the citizens out of the building where the Oasis leaders reside and oversee operations throughout the regional sectors of the Desert. It was also stated that guards protect the outer walls allowing or denying access to see the inside of it while on the outside of it are small towns where the workers that had built the Oasis building resides, this is actually proven to be almost incorrect with the assumption that they could have repaired whatever damages that the structure could have sustained in the government was first established. It was also learned that tunnels run underground connecting to other dark ages cities, it is assumed that they ran throughout the entire desert even though most of the tunnels had caved in due to an unknown event.
The Oasis Government holds complete authority over the Great Kanto Desert to the point that even a contract that has the seal of the government could be ripped up regarding it of no importance when necessary if involving investigations.
Not much is known about the government's technology but it has been shown that they use tanks and armed tankers to when either in military battles or transporting something important. It is also said that they hold the originals weapons that are made in the anime with them having been found in the ruins.