Can this be challenged?
 

A touch is one of the allowed challenges. This is usually challenged on plays where there may have been a touch on a block before going out of bounds.

But if there's a bang-bang play at the net, can a team challenge which player touched the ball first? For example. . .

Team A's back-row setter jumps and sets the ball while she is in front of the attack line and the ball is entirely above the height of the net. The set drifts into the plane of the net where Team A's hitter and Team B's blocker contact the ball at almost the same time. The R1 rules that the blocker touched the ball first and calls an illegal attack. Can Team A request a challenge to see if the hitter contacted the ball before the blocker did?

That's a question of a touched ball, but is the challenge applicable here?

If R1 judges (a) the ball is in the plane of the net and (b) A1 has a body part higher than the top of the net (both are judgments which cannot be challenged), then what does it matter? Either A1 touched it first and it's an illegal attack or B1 touched it first and it's an illegal block.

Whether either one touched it can be challenged, but if that's not in doubt, ...

But the question is what if A2 touched it before B1? That would eliminate the illegal attack. So can the officials review if A2 touched it first? It's a "touch" decision. I'm wondering if it falls into the touch category for review.

I think so.

The officials should determine, prior to taking the challenge, if the result of the challenge would remove how the point would go. If they determine, "Ok, if the other person touched it first, it would be illegal block instead," then we're not going through the challenge. Getting the wrong person touching it, in this case, doesn't constitute a get out of jail free card.

They're still working on it, but the original question very well may wind up being a valid challenge in terms of "are we calling a double or not." Stay tuned...