Although a soccer kick is a foul when delivered to the head in the Unified Rules of Mixed Martial Arts which prevail in North America, the technique was commonly employed in Pride Fighting Championships in Japan. Fighters Wanderlei Silva and Mauricio Rua were notable practitioners of the soccer kick in MMA. Under the Unified Rules, some MMA fighters attempted to use tactics with the "kicking the head of a grounded opponent" rule, which defined a fighter as grounded if they had any part of their body apart from their feet on the ground. This meant that fighters, such as Jon Jones, would often try to provoke illegal soccer kicks by putting their hand on the ground or as a way to avoid strikes such as the soccer kick after a failed takedown. However, in 2013, referees were encouraged to interpret the rules that if a fighter is deliberately intending to provoke an illegal soccer kick and one was used, then the referee could decide that it was a legal move.