[Ref in PA]

I am going to disagree with Tony on a couple of points he has made.

1. "The offensive player isn't required to stay within his vertical plane, but the defender is. And if he doesn't, he is no longer in a legal guarding position. Read 4-44" No where in 4-44 does it say the defenders loses his legal guarding position by his jumping to a new spot. He does lose his rights to verticality, but not LGP. He is now a defender, moving to a new angle from which to defend his/her opponent. It may not be a good angle, but as long as the principles of LGP are kept, the position is maintained. In fact, it happens all the time. Picture a defender sliding sideways with the offensive players at a very fast pace. There will be moments when both of the defenders feet are off the floor.

For my rule, I cite 4-23-3.
"4-23-3 After the initial legal guarding position is obtained:
a. The guard is NOT required to have either or both feet on the floor or continue facing the opponent.
b. The guard may move laterally or obliquely to maintain position, provided it is not toward the opponent when contact occurs."

A defender is moving in a path (in the air), not toward the offensive player. Granted, by jumping the defender is not moving very fast, but the offensive player still runs into the defender. Is the contact the defender's responsibility?

Or consider this example. As the offensive player is driving toward the basket, the defender has established LGP in the path between the offensive player and the basket. As the offensive player nears, the defender jumps up, slightly backward, leaving the verticle plane, the offensive player does not alter course and makes contact. Who will the foul be on? If on the offense, what makes this situation different in your eyes? If you would call this on the defense, then we just plain disagree about being able to maintain LGP.