In addition to illegally parking his truck, Briscoe Darling is in the process of committing a 907. That's the code for "dipping a hat in a horse trough." In this case it's the David Mendelbright Memorial Horse Trough, which has a plaque that reads "Let no horse go thirsty here."
Once Andy makes him aware of his violation, Briscoe is quick to indicate his cooperation. "There ain't a horse in sight, but if one comes along, I'll give him the right of way."