Should they pick up the poop?

This is a rural neighborhood – no streetlights, no sidewalks, no sewers. Town law says people must pick up their dog’s poop but on this road nobody bothers. As long as it is not in front of someone’s mailbox or driveway, nobody cares.

Recently some “equestrians” have discovered the peace and tranquility of our dead-end road. They are teenage girls in fancy riding clothes and ride here on weekends when the weather is nice. They stroll along and drop massive amounts of poop wherever their horses decide to go – always in the middle of the road. Cars run over it and smear the mess in front of our driveways and mail boxes. It gets tracked into our driveways.
One horse dropped a pile on the fishing bridge where people fish. For weeks that load sat there next to fishermen until the rain finally washed it away.
The “equestrians” have such a high and mighty, smug look about them as if they are saying: “Tsk Tsk! Look at this disgusting neighborhood. They leave horse poop in the middle of the road. That is certainly not my horse’s mess.” Arrogant.
So far, a plop has not landed in front of my house. Good thing because I am tempted to collect a load and deposit on their Lexus LX.
A couple of neighbors have suggested we discharge a firearm or two (that is legal here) in our back woods when they are on the road. The noise might discourage them.
What would you recommend? Should they be required to pick up the poop their pets drop?
(I’ll leave this in social since the subject matter is so ripe.)

I am well aware that compared with the problems others have this is a small issue. But it is a big issue here.