All of the major codes have provisions regarding team possession in cases of simultaneous gain of possession by opponents, so what the question boils down to is whether to prefer hands over legs if it comes down to a judgment of "control", or whether to simply invalidate possession via the legs. So let's see what they say about player possession of a ball; some of these quotes may be outdated, so adjust as necessary if you know of any more recent:
- Fed bases possession on the ball's being "held or controlled by a player".
- NCAA goes by "holding or controlling" it.
- NFL goes by "firm grip and control" of it.
- Football Canada and CFL say "firmly held in the hand or hands, arm or arms, leg or legs, or under his body".
I'm not sure how seriously the distinctions between the codes are to be taken, officials being wont to apply general principles in some cases, but let's take them at their words.
The Canadian rules are the only ones making explicit an apparently equal status between holding by the hands and legs.
NFL and Canadian rules are the only ones to have a firmness criterion in there.
Fed & NCAA admit of
either holding or controlling the ball, rather than NFL's requiring both, as a means of possession.
My understanding of "control" is that only one person at a time can be said to have it over the ball.
So how to rule on this case? It is conceivable that the Fed, NCAA, and NFL rules did not contemplate a between-legs wedging of the ball as "holding" or "gripping" it. However, Fed & NCAA would allow it as possession if that's merely sufficient to control the ball, while under NFL rules I'm not sure.
The firmness criterion applied by NFL & Canadian rules might favor the hands player vs. the legs player. It is also likely that when one player has hands on the ball and the other just legs, NFL's requirement of control would favor the hands.
So here's how I'd rule:
In Fed or NCAA, sole possession by the hands player unless the legs player has control of the ball, in which case he has sole possession.
In NFL, ball is still loose.
In Canadian rules, if both are firm, simultaneous possession. Otherwise, judge by firmness.