ABC votes to remove '12-6 elbow' ban, redefines grounded opponent

The Association of Boxing Commissions and Combative Sports has officially removed one of the most unpopular rules in the sport of mixed martial arts.

The ABC voted to remove a longstanding ban on "12-6 elbows" from its unified rules, effective Nov. 1. The 12-6 elbow has been defined as a "straight up, straight down elbow strike" to a grounded opponent. The rule has been controversial in that it places an extraordinary amount of discretion on the referee in real time, and its value towards fighter safety is debatable.

Individual state athletic commissions will still have to approve the change, which is likely.

The 12-6 rule has not come into relevance very often, but it is behind the most controversial loss by disqualification in MMA history: UFC heavyweight champion Jon Jones ' 2009 defeat to Matt Hamill , which remains the only loss of Jones' career. Jones was dominating Hamill when he landed several elbow strikes from full mount. Referee Steve Mazzagatti stopped the bout and ruled the elbows illegal.

Jones (27-1) appealed the result but was unsuccessful. The loss was so controversial that the UFC has even made efforts to overturn it, to no avail. Jones responded to the rule change via social media Tuesday.

"Undefeated then, undefeated now," Jones wrote on Instagram . "Dana White, we gotta get that loss out of the history books."

In addition to removing the 12-6 ban, the ABC also redefined a "grounded opponent" in MMA as a fighter who has "any part of their body other than hands or feet" on the canvas.