A day after Dustin Johnson won the U.S. Open despite a rules debacle, the USGA told ESPN it would “like a mulligan” for its “big bogey” that caused the mess watched by millions.

The same day, the Hawaii State Women’s Golf Association and Foundation held their second rules “study session.” It was a perfect storm, particularly with the HSWGA’s interactive format encouraging questions that often created even more questions.

The fact is, as pretty much everybody who cares about golf discovered Sunday, the 231-page Rules of Golf 2016 book filled with tiny type and the accompanying 585-page Book of Decisions still — incredibly — leave a huge gray area in the game.

There are so many options and interpretations that no one can honestly say they know ALL the rules of golf.

Not the pros and not the guy dedicated and educated enough to earn the right to officiate at the U.S. Open. He exonerated Johnson after his ball moved on the fifth green, and Johnson said he did not cause it.

And not the other high-ranking USGA officials who overturned that official’s decision and penalized Johnson after his round, informing him on the 12th hole that he “might” be penalized.

That left the first-time major champ — who shared the lead as late as No. 13 — and those chasing him in a state of confusion, along with anyone following our national championship. The USGA admitted to “a distraction.”

Johnson ultimately won by three, saving the USGA even more humiliation on the heels of last year’s debacle at Chambers Bay, which golfer/broadcaster Dottie Pepper called “a travesty of a golf course.”

Rory McIlroy characterized Sunday as “Amateur Hour with the USGA.” Jack Nicklaus told Johnson “I thought what you did with all that crap they threw at you was pretty good.”

The timing was actually ideal for the HSWGA’s free-flowing format, designed by Hawaii Golf Hall of Famer Bev Kim. After sending participants eight homework questions beforehand, she and five HSWGA rules officials took questions for two hours Monday.

Then they moved out to Moanalua Golf Club’s ninth hole for up-close-and-personal perspectives about hazards, drops, out-of-bounds areas, the putting surface and bunkers.

“It’s not a class, just a study session,” Kim emphasized. “I want them to learn how to read the book. We’re not teaching rules, we want them to learn how to find out for themselves.

“I’ve been to these USGA-sponsored things where they go through page by page. I sit there and mostly fall asleep. I don’t want to sit through those things so I thought we had to do something different.”

Last year’s first “study session” was called “What Now” and immediately filled its 50-woman limit. This year was “What If” and filled up just as fast, with about half returnees.

“Surprisingly, the ladies really want to learn … ,” said Kim, inspired by the “looks of enlightenment” Monday. “I liked the enthusiasm; they really wanted to be here.”

What they learned, as Dustin Johnson did Sunday, is that the game’s 34 rules are detailed and open to vast interpretation. Did you know …

>> Coal is a loose impediment, but charcoal a movable obstruction;

>> You can mark your ball with anything, and on any side, as long as you replace it in precisely the same spot, and;

>> You can use your clubs for support getting in and out of bunkers and hazards.

Hopefully you will get the rules right, but often there’s a chance you simply won’t be sure. Or, as the USGA put it Monday, “the championship deserved to have clarity at that time, and simply put, we didn’t provide it.”

If you don’t at least try to find clarity in the rules, you are only hurting yourself, and the game. Kim’s plan was to reach out to “the inexperienced and eager, the curious and anxious, the cautious and motivated.” She warned “the easiest and quickest way to learn a rule is to break one and be penalized for doing so,” then insisted the “study session should be less painful.”

Apparently it was.

“I always think you can never remember all the rules, even the rules people have to go back,” said Shera Hiam, who attended Monday. “For me this is a good refresher.

“Every time I come I learn something. I think I get more confident knowing the rules so it’s good I did it. Too bad I didn’t do it before Jennie K.”

In other words, to protect the game, yourself and the field — if you have to call a rules violation on someone else — it makes sense to try to find vivid colors in golf’s gray areas.

If all else fails, Kim points at the game’s three basic principles, located inside the Rule Book’s cover:“Play the ball as it lies, play the course as you find it, and if you cannot do either, do what is fair. But to do what is fair, you need to know the Rules of Golf.”

That might be the real rub of the green, but Kim makes it a bit simpler.

“How do you play so it’s fair?” she shrugs. “That’s the bottom line, that everybody plays the same way.”

The USGA has an email address (comments@usga.org) and phone mailbox (908-326-1857) to receive comments about what went on Sunday.