As I mentioned in this followup to the Kentucky case last week, whether or not it is illegal to ride a horse while under the influence depends on state law, and there are other things the rider could be charged with anyway. Both of which are demonstrated by this case in Florida, in which a 29-year-old man who "urinated on a lawn before riding off on a horse" has apparently not been charged with RUI.
His drunk-riding problem almost solved itself, because either he or the horse then chose to ride down the middle of some train tracks that were soon to be occupied by a southbound train. You'd think at least the horse would have been smart enough to get off the tracks, but police said they had to stop the train to ensure the pair would not be run over. (Not sure why they didn't just go get him off the tracks; seems easier than stopping a train.)
According to the report, the man eventually fell off the horse and ran into the woods, where he was later "found by police dogs," a phrase that sounds a whole lot more peaceful than it probably was.
He was charged with disorderly conduct, resisting arrest without violence, "fleeing and eluding" (although it seems like he fled, but didn't elude), and cruelty to animals. I noticed there was no DUI-type charge, and this could be because under Florida law, DUI only applies to the driver of a "vehicle," and "vehicle" is defined to include "[e]very device, in, upon, or by which any person or property is or may be transported or drawn upon a highway, excepting devices used exclusively upon stationary rails or tracks." I personally think an animal is not a "device," but case law may have held otherwise (note implied disclaimer).
On the other hand, the same chapter has a section titled "Applicability to animals and animal-drawn vehicles," which sounds promising but ends up being confusing:
Every person driving an animal-drawn vehicle upon a roadway is subject to the provisions of this chapter applicable to the driver of a vehicle, except those provisions of this chapter which by their nature can have no application. The provisions of this chapter applicable to pedestrians … apply to any person riding or leading an animal upon a roadway or the shoulder thereof.
Obviously, an animal is not an "animal-drawn vehicle." (Unless one animal is pulling another, maybe, but now you're just being ridiculous.) So despite the title, the actual words of the statute support the interpretation that the vehicular provisions don't apply to animals being ridden. (This Clearwater DUI attorney agrees but says the jury is still out in Florida.)
Interestingly, Florida also now has a law permitting someone with a valid driver's license to "operate an autonomous vehicle in autonomous mode." (California passed a similar law yesterday, so these are apparently on their way whether you like it or not.) Setting aside for now why you should need a driver's license to operate something that operates itself, if an animal were included in the definition of "vehicle," you might be able to argue that you were just "operating it in autonomous mode" while you were fast asleep on its back.
That probably wouldn't help you with the RUI charge, but I'd still enjoy hearing you make the argument.