Explained: The golf rule that cost Rory McIlroy two shots at Spyglass Hill

Rory McIlroy forced a smile as he admitted a misunderstanding of the rules cost him two shots at the 2024 AT&T Pebble Beach Pro-Am. 

McIlroy was playing his first round at Spyglass Hill and went from the top of the leaderboard to the bottom half of the field after returning his scorecard.

The 34-year-old's mistake arrived on his 16th hole of the day - the par-5 seventh - after he pulled his tee shot left underneath a tree. 

McIlroy opted to take an unplayable lie and walked back several yards in line with the hole. He then dropped one club length to the right. 

That provided the Ulsterman a clear shot up the fairway and he later went on to make what he thought was just a sloppy bogey. Instead it was a triple. 

Under a previous version of the rules of golf, in 2019, McIlroy's actions wouldn't have been a problem. But the rule was rewritten in January 2023. 

That change stipulated that a dropped ball can come to rest within one club length in any direction - even forward. 

However the drop has to originate on a line from the flag stick. 

This is covered under model local rule E-12 as part of modifications to rules 14.3b, 16.1c(2), and 17.1d(2).

Rory McIlroy has been assessed a two-stroke penalty after this drop on the par-5 seventh hole. pic.twitter.com/7PtnytRc5t

— PGA TOUR (@PGATOUR) February 1, 2024

Stephen Cox, the vice president of tournament administration, told reporters the infraction came to light through the Tour's video review group. 

"The current rule, which was rewritten in January of 2023, requires the player to go back from where his ball was in line with the flag, this was certainly in his case, and then drop the ball on that line," he said. 

"The ball then, once dropped, can then roll up to a club length in any direction before a re-drop is required. That is the current rule.

"Unfortunately, Rory proceeded under the rules as they were pre-2023, which was you go back on the line and then you would measure one club length off the line in either direction as long as it was no nearer the hole and drop it within that club length.

"So, in other words, you could drop it off the line."

He added: "I think in Rory's case, he was sort of operating in the old rules.

"As soon as I started talking to him about it, I think the penny dropped that he had proceeded under the old rules and he was totally accepting of the fact that he played from the wrong place and he got the two penalty strokes."

What McIlroy said: 

Watch:

Rory McIlroy explains why he received a two-shot penalty at the AT&T Pebble Beach Pro-Am  pic.twitter.com/4cgOCtyjrT

— Sky Sports Golf (@SkySportsGolf) February 2, 2024

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