taunting penalty negates a TD

[Redseal]

The situation happened in a game i was not at, but saw the film.

Team A's receiver is running toward the endzone on a long pass play. When the receiver with the ball gets near the 3 yard line he reaches the ball toward the endzone. He was several steps in front of the nearest B player. He then scores a TD.

Trailing official throws a flag for taunting. The officials enforce the foul from the spot (the 3 yard line) and A has first and 10 from the 18 yard line.

I am not complaining about the play or the enforcement of the penalty. I am just curious if that is the correct enforcement.

Can someone tell me which rule covers this situation?

Thanks