Can you prevent the repo man from tresspassing?

According to the Federal Trade Commission, in nearly every state, the repossession laws allow the agent to come onto your property to locate and remove the vehicle.

They are not allowed to break gates, fences, garage doors, etc.

They are not allowed to threaten or intimidate you.

They must respect your personal property in the vehicle. In California, for example, they must report to you within 2 business days a list of the personal items seized and instructions on how you can recover them. They do not have to return certain dangerous or illegal items, and may turn items over to the police.

The exact laws vary from state to state.