Three hunters are the first to be arrested in Northamptonshire under the 2004 Hunting Act.
The three, aged 17, 23 and 35, were arrested after police received reports of people hunting with dogs in a field between Horton and Brayfield on Sunday.
Two men have now been released on police bail. The 17-year-old was dealt with informally, police said.
Officers also seized a 4x4 vehicle and an estate car, which are now being forensically examined.
The operation, which focused on the Castle Ashby, Hackleton, Horton and Piddington areas, involved the use of marked police 4x4 vehicles and quad bikes.