After the Time out!
 

Rule 7-2-1 Stipulates after the ball is marked ready to play, each player of A who participated in the previous down and each substitute for A must have been, momentarily, between the 9-yard marks, before the snap.
My question is after a Time-out, does this rule apply?

Yes, before any play this rule applies. Many feel that if the player is covered they will let this go, but have some conversation with the player to let them know they must be inside the nine yard marks at some time after the ready.

Yes, otherwise a team could have a conference during the time out and then have one player remain just inbounds right by the sideline and hope the defense misses seeing him. The purpose of the rule is to eliminate the hide out play.

That being said, many will not have a flag for this if the end is covered the whole time by a defender. It is mostly the hideout play they are looking for. It is pretty easy however, for the wing to simply tell the player to get inside the numbers until the RFP is blown.

Agree - No real need to flag this - just tell the player to move inside the numbers until the RFP.

Last year in a playoff game I had this after a TO and I was preventative officiating my tail off to get the wideout inside the tick mark even though he was covered, and I did not toss the flag, but my preventative officiating got me in trouble as the corner demanded the flag and so did his coach behind me, even to the point he asked for a coach-referee conference and we had to "correct" my non-ruling.