Offensive encroachment??

[ML99]

I had a situation - REC lined up far in the neutral zone and didn't listen to me to step back.

1) what would you do in this case - if the player doesn't listen to you? kill the play before the snap? flag it?

2) what to do if the player readjusts and moves back - at the same time the snaps starts.

3) what to do if the player readjusts and moves back - at the same time the snaps starts + another player is in motion

I threw a flag since the play started and he was 1-2 yrds in the neutral zone at the snap. When I reported to the HR he asked me for the foul and I told him enchroachment Offense. He replyed "why didn't you kill the play before the snap - we can't give them a penalty now after the play is over".