Deep Question of the Day (Airport Edition)

What is the protocol on handicap stalls in public restrooms? Are there laws protecting such spots from being occupied by non-handicap individuals?

The way I see it, there are two possibilities: it's either a stall specifically for handicapped persons in much the same way as a parking space is, or it's just another stall that has extra room for people who need it. Really, since there is no enforcement mechanism (aka potty meter maids), you kind of have to figure that it's the later possibility.

But how does society view this? If you are waiting in line to use the bathroom in a public restroom, and a person with some sort of physical disability comes in, does that person get to jump to the head of the line if the handicap stall becomes available? Does that person have to wait just like everyone else? Does that person throw a fit, as I've seen other individuals do in the case of parking in a handicap space (a case in which it is entirely understandable - as Denis Leary self-prescribed, it makes you an "asshole-li-o-li-o-li-o-li-o-li-ole")?  What if there is no one else in the bathroom when you get there? 

I mean the handicap stall is, as I've heard one comedian put it, like the Cadillac of public restroom facilities. So I would assume when you can ride in the Cady, you ride in the Cady. But I'm just interested in what people think the rules are for this seemingly ambiguous area.
 
UPDATE:  Upon having access to the internet again, it looks like Slate had a little discussion about this a decade ago.  The sparking letter and subsequent conversations here and here.  Seems like people can get pretty heated about this.   The underlying paradox is this:

It is a bit of an ethical conundrum that the handicapped want fairness, but fairness for them sometimes results in unfairness to others. Perhaps this is an acceptable trade-off, given the particulars.

The most informational tidbit, however:

Sorry to inform you that in California it is a finable offense to use a handicapped-designated restroom stall if you're able-bodied. The fine for the first offense is $271. I was riding my bicycle on the state beach at Huntington Beach and was arrested and given a ticket, which the court has upheld--in the winter the beach maintenance closes all but the handicapped facilities, so I guess you are supposed to use the landscape.