Fun With Up And Down ...

[Nevadaref]

The legality of this play under NFHS rules depends upon whether or not a defender dislodged the ball. If a defensive player knocked the ball out of the offensive player’s hands he may catch it in midair and return to the floor without penalty. However, if the ball simply slips from his grasp after he has become airborne, he may not regain control in the air and return to the floor as that is a traveling violation.
Note: NCAAM rules differently on the second part. Recently, that level issued an interpretation which deems this action legal. The old NFHS ruling of a travel can be found in this forum’s past Interps archive.