If as a result of the removal of Contested status there are Units located at an uncontested Battlefield that their controller does not control, their controller applies Contested status to that Battlefield.
§ 323.11.a Core Rules PDF (officieel)
§ 323 When a Cleanup occurs, the following Tasks become Outstanding in the order described:
§ 323.11 8. Remove Contested status from each Battlefield without Units controlled by the player who applied Contested to that Battlefield and without a Showdown or Combat ongoing there.
