I don't know about prevailing, but we try and move everything we can into the false start category. Its much easier to kill a play than it is to bring back a touchdown. Plus, it takes less time and rarely, as long as something looks wrong with the movement, do we hear anything from the coaches. I'm not saying you base everything on that, but its a bonus.

To me, calling NCAA rules which are or may be a bit different than Fed in this area, I'm only going to call a live ball illegal shift if, say, 2 guys were shifting and one stops while the other stays in motion without stopping before and during the snap (may be other similar examples). However, if there is any movement toward the LOS by a player who wasn't already in motion (by himself) at the snap, we're shutting it down. We go over this in pregame as we believe it simulates the start of a play and fits under the false start category. In fact, I had this Saturday. One back starts to go in motion and the other one starts moving toward the line just before and during the snap. False start.

I would love to see a US guy ref a Canadian game. :p

What if it's just part of a shift? If the motion isn't quick, jerky, or some other way simulating action at the snap (such as pretending to play the ball), or seems to have no reason to exist other than to draw the defense, the backs have the right to participate in a shift, which may include movement in any direction. It's not uncommon for team A to confuse team B by starting someone in motion in a way that that player might on many plays be in motion at the snap, and then have other players move, and then have everybody reset, completing a shift. I've seen it countless times by double wingbone or flexbone teams, where they motion the wingbacks or shift them into deep halfback position. That sort of action also used to be seen by teams using what they called a Canadian style multiple offense, where they'd get as close as they could to Canadian motion under USAn rules.

Robert

Yeah, well, last I saw, not even Canadian teams were using Canadian style motion any more. Some time around 1980 they seem to have stopped the coordinated "flying" backfield and just started milling around to disguise the snap count. Now they look like nervous people waiting impatiently for the subway train to arrive and not knowing where the doors will open, or contestants on To Tell The Truth about to reveal who it was.

Robert

On the wings, I definitely leave the backfield to the WH. But I'm going to be the WH three times this year, and I won't have anyone left to give it to! :)

Illegal shift is not more that one person moving at the snap. Illegal motion is more than one moving at the snap. An illegal shift happens when two players are in motion but one of them stops (shifts) while the other one continues his motion into the snap.