Is it illegal for a repossession agent to call the police after you refuse to give him the vehicle and order him to leave your property in Washington State?

No it is not illegal for the repo agents to call the police because if it's a reposession, the lender has a financial interest in the car, and since the pink slip holder of the vehicle (the lender) OWNS the car, the lender has every right to the car since it wasn't paid for. However I'm not completely sure what authority police can exercise. I think the next step a lender can take on an unpaid car is to sue/send to collections, or garnish wages.