Thought I would pull it right from the book:
Article 1 – Seven Players On Line
At the instant the ball is put in play, at least seven players of Team A must be within
one yard, and on their [b]own side of the line of scrimmage[/b]. This does not include the
player in the position usually occupied by the quarterback. Conversely, Team A can
never have more than five players, including the quarterback, in backfield positions.
[b]I never thought of this before, but I suppose this also contributes to the grey area of in motion players being allowed that yard of grace, as it only refers to LOS players, not backfield players[/b]
Article 3 – Identification & Positions
On all scrimmage plays at least five line players, including the centre, shall be
identified as ineligible pass receivers and must be positioned in a continuous,
unbroken line. In addition, one player at each end of the line shall be identified as
an eligible pass receiver.
Any other Team A player is an eligible pass receiver, if so identified by playing number
and, at the snap of the ball, is occupying a backfield position at least one yard back
of the line of scrimmage.
above is where it states that only 5 of the 7 line players are ineligible (tackle to tackle). The rule book actually refers to these 5 as the scrimmage linemen.
as far as why receivers who are sometimes part of the 7 mandatory players on the LOS can get way with turning their heads, moving arms, etc...that only applies to the 5 scrimmage players (tackle to tackle) as they are not in a stance.
Article 2 – Stance
No line player of Team A, except the centre, having assumed a three-point or fourpoint
stance, may legally move the head, body, arms, hand, legs or feet until the ball
Article 3 – Offside At The Snap
Team A players must be completely behind the line of scrimmage, except that the
head, arms and hands of the centre may be in advance of the line of scrimmage.
If a Team A player clearly crosses the line of scrimmage by more than one yard,
prior to the snap of the ball, the officials shall stop the play immediately and apply a
The above applies to LOS players, not backfield players...so yeah...those 7 (min) players have no cushion of grace.
And below is for backfield players (non LOS players)...the grey area part mentioned earlier...allows for overriding of illegal procedure for these guys when in motion, and gives the grey area of the grace yard.
bottom of "Article 4 – Eligibility Of Receiver"...section 4 wrote: NOTE: Notwithstanding paragraph (a) of Article 4, a Team A player wearing an eligible
receiver number, who is in forward motion from a backfield position and within one
yard of the line of scrimmage when the ball is snapped and who crosses the line of
scrimmage at a point at least five yards beyond the offensive tackle position, shall
remain eligible as a pass receiver.
Interesting topic. The CFL rule book definitely has a few areas that are not so black and white. This, and some of the Rouge /other single points are definitely at the top of the list.