The wiki for bare legs states "Use this tag when at least 3/4 of the thighs until the middle of the shins are not covered by clothes." To me this would suggest that you should be able to see in the image that this part of the leg is not covered.
However the tag has been used on quite a few images where some or most of that leg is not even visible in the image. I feel, though, that the tag has no real meaning when used on the likes of post #2356233, let alone post #2785933 or #2641289.
I would like to propose that an extra clause be added to the wiki to state that the section of leg in question must be mostly if not entirely visible on at least one leg, meaning that the leg must be visible to at least to below the knees, and the offending images then removed. I am happy to make the wiki changes and a lot of the post changes myself, but given that there are a lot of images affected (probably a couple of thousand at least) I thought it best to bring it up here first.
This would make it all but mutually exclusive with cowboy_shot, a combination which currently has over a thousand posts (although in some cases like post #3092740 it is cowboy_shot that is used incorrectly, and there are situations like post #3130707 (warning: explicit) where both would stay).
Previous posts:
topic #5683 - where the usage of bare_legs was codified. Noone in that thread brings up how much of the leg needs to be in the image.
forum #93056 - One user posts an argument similar to the one I make above in arguing against an implication, which then is not implemented. There is no further discussion on the topic.