Some controversy has arisen in the past few weeks in mixed martial arts. Back to back UFC main events were derailed after bout ending fouls. One was called accidental. The other intentional. The designation can make a vast difference on bout outcome with results varying (depending on timing and foul designation) of potentially going to the scorecards, becoming a no contest or even a disqualification loss.
But what do these terms mean? The problem is they are not defined. Looking to the laws in leading jurisdictions and also the language of the Unified Rules as published by the ABC does not add clarity. I suspect everyone can agree that if a fighter intends to break the rules and indeed breaks the rules that would be an intentional foul. This can be contrasted with a true accident (for example a fighter throwing a leg kick and accidentally hitting the groin). There is a lot of room in between these clear extremes.
Take, for example, a situation where a fighter throws a knee to the head of a grounded opponent. The fighter throws the strike targeting the head intentionally. If they truly believed the opponent was not grounded is that still an intentional foul? Do they have to throw the strike knowing they are breaking the rule to be intentional or is simply throwing the strike intentionally enough whether or not they knew doing so would break the rule? There is no clarity in the rules. When officials explain why they called certain fouls intentional vs accidental it becomes evident some are using different standards than others.
A general staple in legal interpretation is that ignorance of the law or a mistake of law is no defense. Should the same standard be applied when applying the rules of MMA? Should ignorance of a rule (or mistaken belief whether a rule is being followed) make an intentional foul accidental?
As nothing more than food for thought I would suggest the ABC consider addressing the meaning of these words. Ultimately referees will use discretion in deciding if a foul is intentional or accidental. That is fair. Having referees all use the same standard when exercising their discretion is also fair.
I would welcome the views of others, particularly licensed referees, athletic commissions and those that train referees as to what interpretation should be applied to these terms.
Combat Sports Law 
Hi Ed. I would like to comment as a former MMA and boxing referee. One must also consider whether or not warnings were given. In a recent case on UFC fight night, a bout ended with an eye poke. The offending fighter was previously warned about eye poking as the bout ending poke was a second poke. When a fighter has been warned usually the second situation warrants a taking of a point. However, where that second offense ends the bout with a bout ending injury, then instead of the point the offending fighter is to be disqualified. That did not happen on Saturday night. The referee used his judgment and ruled it accidental. We are relying a lot on the referees to make these judgment calls.