The legality of drinking and riding: Is your horse a car? Are you intoxicated? What state are you in?

The previous post introduced the combination of two of my favorite hobbies: horses and vineyards/wine.
Therefore, I thought it my responsibility to inquire as to the legality of mixing those two hobbies.

Is it a crime to drink and ride?

The headline on this post denotes 3 important questions you should ask before you have your stirrup cup, or two or three of them.

Henry, the 10 year old Appaloosa who has a beer at the local Australian pub every Sunday.
Read the rest of the story here.

You already know that driving a motor vehicle while over the state intoxication limit is deeply foolish, and blatantly illegal.

Some of you may know that riding a bicycle while over the legal limit can result in a BUI (many college students learn this the hard way).

But what about riding a horse while intoxicated?
Some say it's a great way to keep people out of their cars when drinking; after all, how much damage can a horse really do?
But there are other instances where drunk riders have in fact been rather foolish: they ride into vehicular traffic, they ride their horses into pedestrians, or as it happened in Alabama, into police cars while on crystal meth, and refusing to "pull over" the horse upon police command.

For those of you in Montana, you may have seen this ad:

I read an article on statutory interpretation of driving under the influence (you can find it here),
and it seems that for the most part, state laws are rather vague as to what exactly constitutes a vehicle, so most courts will charge you with public intoxication rather than getting muddled in the mess of whether your donkey, mule, horse, zebra, etc. is a vehicle.

But it is troublesome to me that the law isn't clear.

In Montana for example, a vehicle for the purpose of a DUI is something that is not propelled by animal power.  
But under the law, a horse drawn carriage is not a vehicle, even though it is pulled by horse power.  I've seen a few carriage races, and I know I wouldn't want those helmed by an intoxicated driver.

In my state, California, this is how a vehicle is defined:

A "vehicle" is a device by which any person or property may be propelled, moved, or drawn upon a highway, excepting a device moved exclusively by human power or used exclusively upon stationary rails or tracks.

However, while some states focus on "what is a vehicle?", other states, like Texas, focus on whether the intoxicated person was operating a "device," which is typically limited to inanimate objects.

I've ridden many horses that most certainly are not self-propelled (bored, gelded, warmbloods during the summer, anyone?) and they require human power (strong legs!).
And I've also ridden a fair share of highly self-propelled horses (causing such equitation errors as pinching my knee to keep my calf off their side!); those horses would not be safe to myself or others to ride without the keenest focus and clear attention.

Do you know how your state treats a drunken rider?

If you don't, what do you think:
Better to ride drunk than drive drunk,
Slap a RUI on an offender (that's Riding Under the Influence!)