[waltjp]

If the IW occurs during a legal forward pass, snap or legal kick, the down shall be replayed.

If the IW occurs during a backward pass, fumble, illegal forward pass or illegal kick, the team who was last in possession may choose to put the ball in play where the possession was lost or replay the down.

If the IW occurs while the ball is in player possession, the team may choose to accept the ball at the spot where the IW occurred of replay the down.

If an IW occurs during a down in which a penalty is accepted before the IW occurred the IW is ignored.

NF Rules 4-3 a, b and c