From the rule book
33.4 Guarding a player who controls the ball
When guarding a player who controls (holding or dribbling) the ball, the elements of time and distance do not apply.
The player with the ball must expect to be guarded and must be prepared to stop or change his direction whenever an opponent takes an initial legal guarding position in front of him, even if this is done within a fraction of a second.
The guarding (defensive) player must establish an initial legal guarding position without causing contact before taking his position.
Once the defensive player has established an initial legal guarding position, he may move to guard his opponent, but he may not extend his arms, shoulders, hips or legs to prevent the dribbler from passing by him.
When judging a charge/block situation involving a player with the ball, an official shall use the following principles:
• The defensive player must establish an initial legal guarding position by facing the player with the ball and having both feet on the floor.
• The defensive player may remain stationary, jump vertically, move laterally or backwards in order to maintain the initial legal guarding position.
• When moving to maintain the initial legal guarding position, one foot or both feet may be off the floor for an instant, as long as the movement is lateral or backwards, but not towards the player with the ball.
• Contact must occur on the torso, in which case the defensive player would be considered as having been at the place of contact first.
• Having established a legal guarding position the defensive player may turn within his cylinder to avoid injury.
The last point is the relevant one. A player may turn to avoid injury after establishing a legal guarding position.
Secondly a player is entitled to a spot on the floor that is not already occupied by another player, thus if a player is standing in a specific spot regardless of facing the player with the ball or not he/she is entitled to that position. The offensive player cannot just run over a defender because he isnt facing him!This is still a charge.