Can this be challenged?

[bob jenkins]

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, ...