NFL footbball rules question.

At the end of the Saints-Dolphins game the ref called an illegal motion or illegal start(couldn’t hear the ref) penalty on a play where the defense intercepted and scored. The Saints declined the penalty.

But I thought that was a penalty you couldn’t decline. I thought when an offense committed those infractions before the play, the play was by rule dead at that point and the yards marched off.

A false start kills the play instantly. An illegal shift or illegal formation does not.

As does the clock expiring before the snap.

Except at the end of the game when the team committing the foul has no timeouts left. In that context there is also a ten-second clock runoff. If there are less than 10 left, game over.

I didn’t see the play in question, but the philosophy is:

A false start is movement BEFORE the snap, thus is a penalty before the play starts. The play gets called off. (The defense can decline the penalty, but there wouldn’t be any benefit to doing so.)

An illegal shift or formation isn’t a penalty until the ball is snapped. Therefore, it is considered a penalty DURING the play. Thus, the defense can accept the result of the play or accept the penalty.