Out of bounds is about the last legal touch, not who wanted the ball.

How officials decide the ball

1. Decide whether the ball actually became out of bounds. Air space outside the line is not enough by itself.
2. Identify what the ball touched when it became out of bounds: floor, line, player, backboard support, bench, official, spectator, or another object.
3. Find the last player or team to legally touch the ball before that out-of-bounds contact.
4. Check whether another rule happened first, such as a foul, kicked ball, traveling violation, held ball, or throw-in violation.
5. Award the throw-in at the spot required by the active rulebook, with the correct clock and throw-in restrictions.

What counts as out of bounds

The boundary lines are out of bounds. If the ball touches a sideline, end line, the floor outside those lines, or an object outside the playing court, the ball is out. If the ball touches a player who is touching out of bounds, that touch also makes the ball out.

A player is out of bounds when any part of the player's body is touching the boundary line, the floor outside the boundary, or something out of bounds. A player who is airborne is judged by where they last touched the floor. That is why a player may jump from inbounds, bat the ball back before landing, and still make a legal save.

Who gets possession after it goes out

The ordinary rule is last touch. If Team A touches the ball last before it becomes out of bounds, Team B receives the next throw-in. It does not matter whether Team A meant to touch it, whether the touch was a fingertip, or whether Team A had possession before the scramble started.

This is why a defender who knocks the ball off the dribbler's leg can win possession, but a defender who merely slaps the ball out directly may give it back to the offense. Officials are not asking who controlled the ball a moment earlier. They are asking whose touch sent the ball into its out-of-bounds status.

Playing the ball near the line

A ball can be legally played while it is above an out-of-bounds area if it has not touched anything out of bounds. A player may leap from inbounds, catch or bat the ball, and release it before landing out of bounds. Once that player lands out of bounds while holding the ball, the ball is out and the opponent normally gets the throw-in.

The same idea explains many sideline saves. The ball crossing the vertical plane of the sideline is not automatically dead in basketball. The ball is still live until it touches out-of-bounds floor, an out-of-bounds player, or another out-of-bounds object, unless a different rule has already stopped play.

What happens after the whistle

After an out-of-bounds ruling, the ball is put back in play by a throw-in. The spot is usually near where the ball became out of bounds, but rulebooks can move the restart after certain fouls, violations, timeouts, frontcourt or backcourt situations, or end-line plays. The inbounding team must follow the normal throw-in restrictions, including the five-second count.

That restart is separate from the out-of-bounds decision itself. First the officials decide whose ball it is. Then they administer the throw-in, set or confirm the clock as required, and apply the proper boundary, movement, and defender restrictions covered in the inbound pass and five-second rules.

When officials cannot tell who touched it

Sometimes opponents touch the ball at nearly the same time, or the officials cannot determine the last touch with confidence. Many rulebooks handle that as a jump-ball or alternating-possession situation. Some professional competitions may use an actual jump ball in situations where other levels use the possession arrow.

Replay can change this in competitions that allow review of out-of-bounds decisions. Even then, replay authority is limited by the rulebook and timing of the game. In games without review, officials must rule from what they saw and use the prescribed restart if last touch cannot be determined.

Important exceptions

• A foul can come first: if illegal contact occurs before the ball goes out, the foul penalty may decide the restart instead of last touch.
• A violation can come first: traveling, double dribble, an illegal throw-in, a kicked ball, or another violation may stop play before the out-of-bounds contact matters.
• Simultaneous or unknown touch may use the arrow: where the possession arrow applies, a tied or uncertain out-of-bounds play can become an alternating-possession throw-in.
• Clock and replay rules vary: late-game out-of-bounds reviews, correction authority, and clock adjustments are not identical across NBA, WNBA, FIBA, NCAA, NFHS, youth, and local play.
• Leaving the court can matter: some rulebooks restrict players who leave the court voluntarily or gain an advantage by going out of bounds, separate from the last-touch decision.

Common arguments

• "The ball crossed the line, so it is out" is wrong in basketball. The ball must touch something out of bounds, or an out-of-bounds player must touch it.
• "Possession decides the call" is too broad. The usual out-of-bounds decision is last touch, not who had control before the deflection.
• "A player cannot save the ball over the sideline" misses the airborne rule. A legal save can happen from inbounds before the player lands out.
• "The defender knocked it loose, so it stays with the offense" is not automatic. If the ball then touches the offensive player last before going out, the defense may get the throw-in.
• "Every out-of-bounds mistake is reviewable" is wrong. Replay availability, timing, and scope depend on the competition.

What officials look for

Officials position themselves to see the boundary line, the ball, and the hands or body parts involved in the final touch. On tight plays, one official may have the line while another has the deflection angle. They may briefly confer if one has the last touch and another has the out-of-bounds status.

Good officials also avoid guessing from reaction alone. Players often point the other way after any close boundary play. The ruling should come from the official's view of the touch, the player's location, and the ball's contact with the line, floor, or object that made it out of bounds.

Source material

• FIBA Official Basketball Rules
• NBA Rulebook
• Official Rules of the WNBA
• NCAA Basketball Rules
• NFHS Basketball Rules