Star Frontiers Revisited
The Frontier is the area of space colonized by the Core Four races, governed federally by the United Planetary Federation where Pan Gal emerged as the universal trade language. Each planet governs its own affairs with its authority generally extending only as far as its outer orbit with a few exceptions due to colonial territories predating the foundation of the UPF.
In practice, those planets fielding their own space militia will police the out system to protect their planet’s interest and regulate commerce. By treaty this is Space Fleet’s responsibility but the fleet is not large enough yet to effectively do so.