The Exchange

The Exchange is an intergalactic crime syndicate from the Star Wars universe - mostly controlled by the Hutt Cartels, with it's unofficial capital being Nar-Shadaa. The Exchange can in many ways be compared to a nation, as it has it's own laws and it's own ways to recognize it's members, not unlike the way a nation recognizes it's citizens. 
The Exchange is originally from Star Wars, but if you replace the Hutts with some other powerful cultural elite, they can work in any space age science fiction setting. 
In the Star Wars universe, a substantial portion of the very large space region known as the Outer Rim is more or less under complete control by the exchange - the Hutt Cartels more specifically, and this region of space is known as Hutt Space and is considered the actual seat of the unofficial nation of the Exchange. 
To briefly explain how the exchange operate, they're not a gang or directly involved in crime, rather any gang that ever expands their influence widely enough - in most cases when their presence is found on more than one planet, but in some cases the exchange starts to meddle already when the gang is still planetary. 
The exchange offers a simple deal: Access to exchange resources for paying a cut to the local exchange boss, become the local exchange representative who will enforce exchange rules among other local gangs, follow exchange rules OR be destroyed. 
It's not as much of a black mail as it sounds, as the exchange offers great advantages to it's members.