World No. 1 Jordan Spieth and world No. 3 Rory McIlroy both took to Twitter to express their dismay at the treatment of Johnson.
Jeff Hall, the USGA official who informed Johnson of the possible violation, defended the decision in an interview with the Fox broadcast team, saying that it was only fair for the USGA to tell a player on the course there was a chance he might be penalised after the round.
That way, the player could make decisions about his round knowing that his score might be different (if Johnson thought he was tied, he might lay up on the reachable par-4 No. 17. If he knew there was a possibility he could be one behind, he might try to drive the green).
Of course, the obvious retort is that if you don't know what's going to happen, how can you plan for anything at all? Either assess the penalty or don't. There's no need to wait.
It should be simple: Johnson consulted a rules official walking with his group. That rules official gave the OK that no penalty was committed and that no penalty should be assessed. Voila. That's it. Situation over.
But golf is a sport that loves its rules and has seen a strict interpretation and adherence to all of them. They have cost a player The Masters because he signed an incorrect scorecard. It's had players lose tournaments because viewers at home called up to report violations they'd seen upon replay. Johnson missed a playoff because he didn't know a rule about grounding in a type of bunker.
Luckily for Johnson, the kerfuffle didn't have any impact in the end, as he blocked out everything around him to win the trophy, finishing at five-under for the tournament.
He shot a final round 69 - including the penalty - to finish three shots ahead of Jim Furyk, Shane Lowry and Scott Piercy.
Johnson erased a four-stroke deficit and finished with a birdie at the last to capture his first major title at Oakmont.
The world No. 6 took the lead with two birdies on the front nine as overnight leader Shane Lowry faltered.