A defender is in a legal guarding position (LGP) when they have both feet on the floor and are facing the offensive player they are guarding. Once they are in this position the may move sideways laterally or backward. If contact is made enough for a foul to be called then it has to be a player control foul if the player has the ball or if the player does not have the ball it is a team control foul.. No shots, ball out of bounds at spot of the foul for the defensive team.
Once a player gets head and shoulders by a defender with or without the ball and there is contact enough to call a foul, then the foul is on the defense.
Situation, Player A1 establishes his/her legal guarding position before B1 leaves the floor for a shot or pass and B1 crashes into A1. This is a player control foul if the offesnive player has the ball and it is a charge if the player does not have the ball.
If the defender establishes LGP and then slides over after the offensive player is airborne then this is a block on the defensive player.
Also, after establishing legal guarding position the defender just turns to protect themselves from an air borne offensive player, this is still a charge if the airborne player crashes into the defender.
After establishing LGP the defender backs up while the offensive player is in the air….and if enough contact warrants a foul it is a foul on the offensive player.