College Football/Off sides during on-side kick
In the recent ACC championship game, UNC was called off sides during the final on-sides kick off. Does the rule specify "any part of the body" across the restraining line? If you freeze-frame the play, it is very clear that no feet were across the line (in fact, the closest was nearly a yard behind). Maybe the players head was ever so slightly ahead at the actual time the kickers foot touched the ball. But would that constitute "off-sides?" In such critical calls as this was, why isn't replay used?
Thank you for your question. The short answer is no the rule does not reference any part of the body, it references "the player" which is interpreted to mean any part of the body. Below is a more detained explanation to your questions.
Rule 6-1-2-c states that all Team A players (kicking team players) except the kicker and holder must be behind the ball when the ball is kicked. When there is an on side kick this rule is strictly applied. The officials on the Team A restraining line officiate it as if the line is a vertical plane (Rule 2-12-5) and if the player breaks the plane he is off side. On a deep kick off it is not as strictly enforced by national philosophy - it is enforced but not so technically or strictly as during an onside kick because an on side kick is in close proximity to the restraining lines and Team A would have an unfair advantage during an on side kick to be beyond their line. They already have an advantage in being able to run toward the opponent - a running start, and the knowledge where the ball will be kicked and how it will be kicked. On scrimmage plays we do not allow the defense to be in or beyond the neutral zone prior to the snap because that create an unfair advantage to the opponent. The officials don't just look at the feet. The rule state "the player" must be behind the restraining line so it is any part of his body or equipment [i.e. helmet, face mask, shoulder pad, etc]. Again this restraining line is a hard plane much the same as the goal line so if the ball breaks the plane at the goal line you have a TD, likewise on the onside kick if the player [or any part of his body] breaks the plane he is off side.
The crews working the games yesterday are the best of the best and did a fine job. They do not officiate frame by frame, they view the play in real time with fast moving players. Onside kickoffs are challenging to officiate because players are moving fast toward a hard vertical plane that they cannot cross until the ball is kicked so there are a lot of moving parts and great concentration is required. Officials can find it difficult to tell even standing right on the line whether a player is beyond the plane prior to the kick but experience and training and strict focus dow the vertical plane is how it is officiated. and it is a foul on an on side kick if a kicking team player encroaches with any part of himself into or beyond the line/plane before the ball being kicked.
Thank you for asking this can be a confusing rule especially if you are look to the feet as the terence point which many sports announcers and coaches mistake as the reference point. I hope this explains the rule in detail and why, in terms you can understand. If you are a fan of the kicking team I realize this is a harsh rule but is is applied to create fairness and no extra competitive advance to a team.