A uniformed officer in a patrol car making unrelated inquiries in the area indicated to the driver to stop.
The Hilux did not stop, turned up on a forestry track, and became stuck in a bog in a cleared forestry area.
The officer walked down the slope and approached the passenger's side of the Hilux.
Theobald got out but the officer tried to stop him from checking his dog.
The officer did not know he has no lawful authority to do so.
Matters became physical and Theobald threw at least two punches - both of which connected, resulting in a broken nose and associated bruising and swelling for the officer.
He argued in court it was self-defence.
• Whangārei assault on police: Policeman punched in face, policewoman spat on
Crown lawyer Kyle MacNeil said an aggravating feature was attack to the officer's head that required that Theobald be sentenced to more than a short prison term.
Defence lawyer Emma Priest submitted the least restrictive sentence be imposed.
Judge Noel Sainsbury said the officer was wrong in his assessment of the legal position in that he had no right to tell Theobald not to check on his dog.
"While any citizen can insist on exercising that right, it has an increased risk of causing violence to break out."
Glowing references were submitted to court on Theobald's behalf that spoke of his good work ethic and commendable loyalty to family and friends which, the judge said, left a lot of unanswered questions as to why he committed the offence.
Since Theobald has spent a significant time in custody and has been on electronically-monitored bail for eight months, Judge Sainsbury said he has effectively served his time in prison.