Unclaimed space
Unclaimed space or free space was any region of space that was not claimed or recognized as territory belonging to any one political or independent entity.
The border of the Tholian sector, located in the space between the Tholian Assembly and Federation space was said by Commander Spock to be free space; specifically, space that had not yet been surveyed by the United Federation of Planets in 2268. When this fact was conveyed to the Commander Loskene, the Tholian strongly contrasted his statement, stating that it was the opinion of the Assembly that the area was their territorial annex. (TOS: "The Tholian Web")
In 2372, the IKS M'Char, commanded by Kaybok, stopped the SS Xhosa in its tractor beam in Bajoran space in effort to search the ship for Changeling infiltrators. After Captain Benjamin Sisko of the USS Defiant warned off the Bird-of-Prey, citing that they had no jurisdiction at that location, it, along with the rest of the Klingon task force posed to invade Cardassia Prime, withdrew to just outside Bajoran territory into unclaimed space. Given their new position, Sisko noted that if the Klingons decided to continue searching ships, there was nothing they could do about it unless they tried to stop a Federation or Bajoran starship. (DS9: "The Way of the Warrior")