A year ago my answer to this question would have been absolutely NAY, NAY, NAY! But today I’m a lot less emphatic. I still can’t vote yay, but I’m going with a much more gentle nay. And here’s why.
A few seasons ago, most legging styles resembled opaque hosiery at best. Cotton lycra knit legging styles were more substantial but the overall appearance of leggings was more like tights than pants. For this reason it seemed inappropriate to wear leggings as pants since you might as well have been walking around in your underwear.
Over the years, leggings styles have evolved and some are designed to look more like pants than hosiery. Like pull on Ponte knit pants, motocross leggings and legging jeans. They are thicker and offer plenty of coverage, much like a pair of skinny jeans. These types of leggings can be worn as pants.
So I guess the line has become more blurred. Some leggings styles are fine to be worn as pants whereas others function more like hose. It all boils down to the details and your definition of leggings.
I’m sticking to a more modest vote of “generally nay”, because there are too many tricky caveats associated with a general yay. What about you?