The rules of boxing vary from jurisdiction to jurisdiction, and on whether it is an amateur or professional bout. A violation of the following rules is considered a foul, and can result in a warning, point deduction, or disqualification by the referee:
You cannot hit below the belt, hold, trip, kick, headbutt, wrestle, bite, spit on, or push your opponent.
You cannot hit with your head, shoulder, forearm, or elbow.
You cannot hit with an open glove, the inside of the glove, the wrist, the backhand, or the side of the hand.
You cannot punch your opponent’s back, or the back of his head or neck (rabbit punch), or on the kidneys (kidney punch).
You cannot throw a punch while holding on to the ropes to gain leverage.
You can’t hold your opponent and hit him at the same time, or duck so low that your head is below your opponent’s belt line.
When the referee breaks you from a clinch, you have to take a full step back; you cannot immediately hit your opponent–that’s called “hitting on the break” and is illegal.
You cannot spit out your mouthpiece on purpose to get a rest.
If you score a knockdown of your opponent, you must go to the farthest neutral corner while the referee makes the count.
If you “floor” your opponent, you cannot hit him when he’s on the canvas.
A floored boxer has up to ten seconds to get back up on his feet before losing the bout by knockout.
A boxer who is knocked down cannot be saved by the bell in any round, depending upon the local jurisdiction’s rules.
A boxer who is hit with an accidental low blow has up to five minutes to recover. If s/he cannot continue after five minutes, s/he is considered knocked out.
If the foul results in an injury that causes the fight to end immediately, the boxer who committed the foul is disqualified.
If the foul causes an injury but the bout continues, the referee orders the judges to deduct two points from the boxer who caused the injury.
If an unintentional foul causes the bout to be stopped immediately, the bout is ruled a “no contest” if four rounds have not been fully completed. (If the bout was scheduled for four rounds, then three rounds must have been completed.) If four rounds have been completed, the judges’ scorecards are tallied and the fighter who is ahead on points is awarded a technical decision. If the scores are even, it will be called a “technical draw.”
If a boxer is knocked out of the ring, he gets a count of 20 to get back in and on his feet. He cannot be assisted.
In some jurisdictions the standing eight-count or the three knockdown rule also may be in effect.
In other jurisdictions, only the referee can stop the bout.