Police have ordered 28 caravans and vehicles to leave land on Osier Way and at the Swan Business Park in Buckingham.
The order has been issued by police under section 61 of the Criminal Justice and Public Order Act 1994.
Police say: "We believe the occupants of these vehicles have entered this land as trespassers, with a common purpose to reside on the land.
"All reasonable steps had been taken on behalf of the person entitled to possession of that land to ask them to leave."
Although it is unusual for officers to use these orders on private land, police say they have taken these steps following reports of disorder, assault, theft, intimidation and disruption to local businesses on the site.
The force say that a code of conduct had been issued to the occupants of the vehicles but as this was ignored they were forced to take further action.
Although the unauthorised caravans and vehicles have now left the site the police say they are maintaining a presence in the area and have thanked the public for their patience.