RORY McILROY was hit with a bizarre two-shot penalty after breaking a little-known rule.

The golf ace was competing in the opening round of the AT&T Pebble Beach Pro-Am when the incident happened.

McIlroy started well with six birdies in the first 10 holes.

But the four-time major champion followed that up with two bogeys and a double bogey.

McIlroy’s collapse saw him finish one-under par and eight shots behind Thomas Detry.

And it was at the seventh hole where his troubles began.

The world No2 managed to get stuck behind a tree at Spyglass Hill following a dodgy shot.

He declared the ball unplayable as he opted to take a drop.

And McIlroy then appeared to work out a reference line to the hole.

But this landed the Northern Irishman in hot water after he contravened Rule 19.2b of the USGA’s laws.

That’s because McIlroy was deemed to have placed the ball incorrectly, straying too far to the right of his club-length reference line.

He would not have been punished had he dropped his ball within the line.

And the ace was hit with a two-stroke penalty by golf chiefs.

However, McIlroy insists he had not been aware of the law, which was changed a year ago in January 2023.

He told reporters afterwards: “So I took an unplayable on 7and I took it back online.

“Then unbeknownst to me, the rule changed in January 2023 where you used to be able to come back online, take a club length either side.

“That was changed in 2019 to be able to do that. I wasn’t aware that the rule changed again in 2023, so I took a drop thinking of the 2019 rules when everything was sort of changed, not knowing that the rule was changed again in 2023, so got a two stroke penalty there.”

McIlroy added: ‘I feel like my game’s in really good shape. I’m hitting it well, feel comfortable around the greens, on the greens. Yeah, game feels in good shape.

“It was just one of those — I just let it — I had a really score and then just sort of let it get away from me those last few holes. 

“I played really well for the first 14 holes and then obviously had a bit of a bad finish there. But for the most of it I hit the ball pretty well.

“There’s a lot of good stuff in there. Had that run of holes on 6, 7 and 8, but I mean apart from that, I actually played very well.”