Know the BJJ rules: Knee reaping 102 - Foul

Knee ripping – Serious Foul - Penalty

•When the athlete executes the movement in the characteristics mentioned above, moving his foot across the vertical midline of the opponent’s body. The referee shall stop the match, return the position if permitted and issue a penalty to the athletes before restarting the fight.

If you want to read about what type of knee reaping will get you AUTOMATIC DQ

http://www.aucklandbjj.com/2014/09/know-bjj-rules-knee-reaping-101-seve.html