The Dimension Heart Zone of the Goblin Paradise was located in a valley that was reinforced by the humans by building thick walls so the goblins couldn't claim that place or make any trouble.
Within this valley were multiple guard posts, and in the center was built a small size city with simple building structures. These kinds of places in dimensions were known as Sanctum Cities where only humans could enter no dimension creatures.
Furthermore, Sanctum Cities were also the only exit point to the outside world from a dimension, and that's how the Magic Union controlled the flow of dimension-related goods. The people inside had no other choice but to abide by the Magic Union rules if they wanted to get out.
Not only that but within a dimension, those law enforcers were even more overbearing and ruthless. That's why not causing trouble.
