Competition Rules
From a competitors point of view, the contest rules are fairly simple. Which is how we will be examining the rules here. For a complete list of the Judo contest rules please see:
The IJF Detailed Explanation of the IJF Judo Refereeing Rules
Or the IJF Sports and Organization Rules
Basics of the Competition Rules
The contest rules of Judo are setup as a safe way to simulate a fight and allow the students to practice their techniques against a resisting opponent. With this in mind, consider yourself the "good guy", in real life, bad guys rarely attack alone. One of the assumptions of the rules is, the bad guy has accomplices. Therefore, you want to grip your opponent in such as way as to be able to control their shoulders and hips to prevent them from punching and kicking you, and to use them as a body shield, keeping them between you and their accomplices. This is the traditional grip with on hand on the lapel and one hand on the sleeve. obviously, in a Judo match it is just you and your opponent, but this is still the idea. If you have a non-standard grip (e.g. two sleaves or both hands on one side of the body) you must be using it to attack. As long as you are actively setting up and attacking you may maintain this grip. If you find yourself in a position where you can no longer attack, you must switch back to a traditional grip.
In ground work you, in a real fight, you do not want to be on the ground longer than you have to, and you want to maintain the ability to stand up when necessary. As long as there is progress being made, the referee will allow the match to continue in ne waza (ground work).
As the "good guy", your goal is to finish the fight as quickly as possible with a technique that would win the fight in a real situation.
Ways to win your match
Throwing your opponent, with a recognizable Judo technique, from their feet to their back with speed, force, and control. Control must be maintained all the way through the landing for a score to be given. If the referee deems your throw to in one or more of the four areas, but still good enough for a score, you are given a score of waza ari (with technique)
(I will not get into the nuances of the scoring here. You aren't trying to get minor points.), if allowed in your
Pinning your opponent for 20 seconds. While pinning your opponent's back should be generally toward the mat or one of their shoulders must remain in contact with the mat and you must remain free from being entangle by their legs. If you pin your opponent for more than 10 seconds, but less then 20, you earn a score of waza ari (with technique).
If aloud in the division you are fighting in, with a strangulation technique.
if aloud in the division you are fighting in, with a joint locking technique against the elbow.
With a combination of two attacks which were deemed good enough for a score, but not good enough for an ippon (one point). The second waza ari is raised to ippon (one point), waza ari awaseti ippon.
Some common minor penalties (shido)
Being overly passive (not attacking). Remember, you are trying to finish the fight as quickly as possible before the bad guys accomplices show up to help. You don't have time to be passive.
Holding a single sided grip without attacking. While great for throwing, you lack control of your opponent if they were striking.
Being overly defensive (stiff arming, bent over posture). Remember, you are trying to finish the fight as quickly as possible before the bad guys accomplices show up to help. You don't have time to just block your opponent from attacking. You need to attack.
Attacking or blocking your opponents legs while one or both opponent are standing. This rule was created in an effort to get the contestants to stand up where they would be able to defend themselves if their opponent was string.
Attempting to apply a joint lock or strangulation while one of both contestants are standing
Some grave infringements penalties (hansoku make)
Doing these will disqualify you from the match, but you can continue the tournament if the loss doesn't eliminate you.
Receiving a third shido (minor penalty) is awarded as hansoku make.
Using the bottom of the jacket or the belt to strangle your opponent is a grave infringement of the rules and will result in automatic disqualification of the match.
Attempting to apply a joint lock to a joint other than the elbow is a grave infringement and will result in disqualification from the tournament.
Acting against the spirit of Judo. This could include derogatory language directed toward the referee, another participant, or a coach. Another example would be, a contestant who is ahead and is refusing to engage their opponent to prevent them from being able to score.
Some severe grave infringement penalties (hansoku make)
Doing these will eliminate you from the tournament. Yes, even if you were in multiple divisions.
Intentionally trying injure your opponent. This is a grave infringement of the rules and you will be disqualified from the tournament. Throwing or attempting to throw your opponent, applying strangulations techniques, and applying joint locks against the elbow with control are NOT considered trying to hurt your opponent. However, while applying strangulation techniques and joint locks you must allow your opponent the opportunity to tap, and you must release the technique when they tap, verbally submit, or the referee calls matte or ippon.
To "dive" headfirst, onto the tatami by bending forward and downward while performing or attempting to perform a throw.
For Uke, the person being thrown, to intentionally try to land on or block a throw with their head, are any attempts to prevent themselves from being thown which are dangerous for their neck or spine.
Judo Practice Uniform - Judo Gi
The original Judo gi was shorter in the sleeves and pant legs, more closely matching the traditional Japanese Kimono of the day. As Japan adopted more of the customs of the West, and as Judo spread throughout the world, the sleeve and pant length was increased to match that of a business suit. Today the gi sleeves should fall comfortably to your wrists and the pants should hang to the tops of your feet. Since you are providing the equipment for you partner to grip, and your partner is providing the equipment for you to grip, there should be sufficient slack in the gi throughout the arms for your partner to take a grip. The material should be sturdy enough to stand up to being pulled on, but supple enough to be gripped. Your gi should be clean and in good repair. Your belt should be properly and securely tied around your waste, and should represent the color of the official Judo rank you hold.
Contest Area - Shiai Jo
The contest area consists of a safety zone, which the players should generally avoid, and the main contest area. If you and your partner enter the safety zone as the result of attacking action, the referee will allow the action to continue as long as it is safe for you and your partner. Forcing your partner into the safety zone, or entering the safety zone without attacking action will result in a penalty.
Bowing - Rie
When entering the contest area, you and your opponent will bow out of the world as you enter the safety zone. You will then formally bow into the competition area as you exit the safety zone. As you and your opponent approach each other toward the center of the mat, you will bow to each other as a show of respect and take one step forward. This lets the referee know you are ready to being the contest.
At the end of the contest, when the referee awards the match, you and your opponent will take one step backwards and bow to each other. You will each bow out of the competition area and then bow back into the world as you bow off the mat.