This has to be one of the most difficult rules in sports to enforce.

Cricket’s 15-degree rule.

The world’s top-ranked one-day international (ODI) bowler (pitcher) was suspended indefinitely today because studies of his bowling “action” find him breaking the 15-degree rule.

Which is … ?

The rule that states that the angle between the forearm and upper arm — the bend at the elbow, that is — must not exceed 15 degrees, when in the process of bowling.

If you have not seen cricket, the bowler in theory is supposed to have a throwing motion that comes directly over the top, with minimal elbow bending. Less than 15 degrees, anyway.

In strong contrast to baseball, where a pitcher can throw a ball any ol’ way he wants, as long as it gets to home plate. Sidearm, underhand, with as much elbow bend as a guy likes.

Not in cricket.

Guys who would be called “junk ballers” in baseball are most likely to run afoul of the 15-degree rule. “Pace” bowlers, the guys who just try to overpower batters with speed, tend not to bend their elbows much.

But “spin” bowlers, and “off-spinners” (don’t ask me what the difference is), pretty much are trying to throw curves and sliders and cutters and even the screwball.

The ICC can report “suspect actions” and the accused basically has no other recourse but to wait for a scientific analysis of his motion, which is broken down in a lab to see if he is going past the magical 15 degrees mark.

The bowler suspended today, Saeed Ajmal of Pakistan, was reported for a suspect action back in August, and now he is out.

Besides throwing a variety of junk (look how the ball sits in his hand before he bowls it), he also throws a sort of mystery pitch known as the doosra — which some observers believe to be illegal every time it is thrown.

(If I understand correctly, it comes out of the hand while the palm is facing the bowler’s face, sort of over the top of the fingers, and is deadly, if accuracy is there.)

At The National, where we cover cricket in depth, a close watch is on during what seems like a crackdown on suspect actions — bowlers whose elbows bend too much.

The suspicion is that the sport’s ruling body, the International Cricket Council, would like to see more runs in the game.

Sort of like when baseball had it’s “chicks dig the long ball” campaign, 15 years or so ago, when the long ball was often provided by chemically enhanced batters.

But cricket, too, has noticed that fans seem to react to fours (balls that roll to the boundary) and sixes (balls that land over the boundary), and pundits suggest that hamstringing off-spinners is a way to increase scoring.

Maybe they are right. Because today they brought down one of the world’s best junkballers, whose defense is that he has an unusual elbow, stemming from an accident 15 years ago.

Anyway, Saeed Ajmal is suspended until he can demonstrate — at a testing facility in Brisbane, Australia — that he can bowl without bending his arm too much. He could be out a year, which is bad news for Pakistan, with the ODI World Cup coming up early in 2015. He is likely to miss that, and almost certainly will miss Pakistan’s matches with Australia to be played in the UAE next month.

(Pakistan is not allowed to play international matches at home since the 2009 terror attack on the Sri Lanka team, while in Lahore. The UAE almost always serves as its home away from home.)

Rest assured, this is very big news in cricket. And enormous news in Pakistan.