some articles that may help:
Art. 11 Location of a player and an official
11.1 The location of a player is determined by where he is touching the floor.
While he is airborne, he retains the same status he had when he last touched the floor. This includes the boundary line, the centre line, the three-point line, the free-throw line, the lines delimiting the restricted area and the lines delimiting the no-charge semi-circle area.
Art. 23 Player out-of-bounds and ball out-of-bounds
23.1.1 A player is out-of-bounds when any part of his body is in contact with the floor or any object other than a player, on, above or outside the boundary line.
23.1.2 The ball is out-of-bounds when it touches:
• A player or any other person who is out-of-bounds.
• The floor or any object on, above or outside the boundary line.
• The backboard supports, the back of the backboards or any object above the playing court.
23.2.1 The ball is caused to go out-of-bounds by the last player to touch or be touched by the ball before it goes out-of-bounds, even if the ball then goes out-of-bounds by touching something other than a player.
23.2.2 If the ball is out-of-bounds because of touching or being touched by a player who is on or outside the boundary line, this player causes the ball to go out-of-bounds.
23.2.3 If a player(s) move(s) to out-of-bounds or to his backcourt during a held ball, a jump ball situation occurs.
And the final comment from the FIBA casebook:
ARTICLE 23 Player out-of-bounds and ball out-of-bounds
23-1 A4 is dribbling the ball near a sideline. A4 loses his balance and steps out of bounds without touching the
ball. A4 returns to the court and continues his dribble. Is this legal?
Yes. In order to be out of bounds, the ball has to touch the floor out of bounds, a player or any other person
who is out of bounds or any object on, above or outside the boundary line. A4 did not touch the ball while
out of bounds. Therefore, neither A4 or the ball were out of bounds.