I haven't seen the details of this strange rule posted yet. It took effect for the 2016-2017 season. Here is the rule:
Rule 4, Section 39, Article 1c. The space that a player may legally occupy is defined by an imaginary cylinder surrounding the player and which extends from the floor to as far above the player as he can jump or extend his arms and body. The diameter of the cylinder shall not extend beyond the hands/arms on the front (the arms bent at the elbow), the buttocks on the back and the legs on the sides. These dimensions may vary according to the height and size of the player.
Rule 4, Section 39, Article 1k. The offensive player must be allowed enough space to make a normal basketball play. The defense may not invade the vertical space of the offense and make illegal contact when the offensive player is attempting a normal basketball play. A normal basketball play in this context includes shooting, passing, dribbling or pivoting.
Per an article from 247 Sports, a Rules Committee spokesperson had this to say:
"The cylinder interpretation took effect ahead of the 2016-17 season. Following the NCAA Officiating Clinics last October, rules committee secretary-rules editor Art Hyland offered further commentary on cylinder plays indicating that Brooks could have potentially been called for a foul.
Hyland wrote: "If the defender has invaded the space of the offensive player and the offensive player attempts a "normal basketball play" (defined as attempting to shoot, pass, dribble, or pivot) by moving his elbows from side to side either above the shoulders or below the waist with the forearms more vertical than horizontal, any resulting contact (other than incidental contact) to a defensive player caused by the swinging of the elbow shall result in a foul on the defense."
Roy Williams had this response after a controversial call in the 2019 Tournament:
""In my opinion, and I don't care what anyone else says - they can give me all of this flowery description - it's BS," the Hall of Fame head coach said. "He's standing there and he's not doing anything with his hands up. He's straight up in where he can be and the guy's elbow hit him in the mouth. I disagreed at that time. I wasn't asking for a flagrant foul. I didn't think it was that, but it's bad when Garrison bites a guy on the elbow. 'You fouled a guy. You bit his elbow!' Come on now.
"But I think the rules committee needs to look at that. It was a factor in the game. It took out our best defender for the entire rest of the first half. I think the intent of the rule is okay, but what we're supposed to be concerned about more than anything is player safety. I think when the rule was the way it used to be, you could go to the monitor, you could call a flagrant, you could even eject the guy, you could call a technical even if he didn't make contact. That made youngsters be more aware of the rule and more aware of that type of behavior… You can rip the ball through high or you can rip the ball through low and you can get your guys to back off him.
"For 31 years, I've taught our guys to rip the ball through low. I think that's the safest way. You don't put anybody in harm and you can get people off of you. And I don't think it was necessarily that, but I think he turned around and he took up Garrison's face with his move. Now again, I read all of this pretty neat definition, but I don't believe it. I don't care what anybody says."
Rule 4, Section 39, Article 1c. The space that a player may legally occupy is defined by an imaginary cylinder surrounding the player and which extends from the floor to as far above the player as he can jump or extend his arms and body. The diameter of the cylinder shall not extend beyond the hands/arms on the front (the arms bent at the elbow), the buttocks on the back and the legs on the sides. These dimensions may vary according to the height and size of the player.
Rule 4, Section 39, Article 1k. The offensive player must be allowed enough space to make a normal basketball play. The defense may not invade the vertical space of the offense and make illegal contact when the offensive player is attempting a normal basketball play. A normal basketball play in this context includes shooting, passing, dribbling or pivoting.
Per an article from 247 Sports, a Rules Committee spokesperson had this to say:
"The cylinder interpretation took effect ahead of the 2016-17 season. Following the NCAA Officiating Clinics last October, rules committee secretary-rules editor Art Hyland offered further commentary on cylinder plays indicating that Brooks could have potentially been called for a foul.
Hyland wrote: "If the defender has invaded the space of the offensive player and the offensive player attempts a "normal basketball play" (defined as attempting to shoot, pass, dribble, or pivot) by moving his elbows from side to side either above the shoulders or below the waist with the forearms more vertical than horizontal, any resulting contact (other than incidental contact) to a defensive player caused by the swinging of the elbow shall result in a foul on the defense."
Roy Williams had this response after a controversial call in the 2019 Tournament:
""In my opinion, and I don't care what anyone else says - they can give me all of this flowery description - it's BS," the Hall of Fame head coach said. "He's standing there and he's not doing anything with his hands up. He's straight up in where he can be and the guy's elbow hit him in the mouth. I disagreed at that time. I wasn't asking for a flagrant foul. I didn't think it was that, but it's bad when Garrison bites a guy on the elbow. 'You fouled a guy. You bit his elbow!' Come on now.
"But I think the rules committee needs to look at that. It was a factor in the game. It took out our best defender for the entire rest of the first half. I think the intent of the rule is okay, but what we're supposed to be concerned about more than anything is player safety. I think when the rule was the way it used to be, you could go to the monitor, you could call a flagrant, you could even eject the guy, you could call a technical even if he didn't make contact. That made youngsters be more aware of the rule and more aware of that type of behavior… You can rip the ball through high or you can rip the ball through low and you can get your guys to back off him.
"For 31 years, I've taught our guys to rip the ball through low. I think that's the safest way. You don't put anybody in harm and you can get people off of you. And I don't think it was necessarily that, but I think he turned around and he took up Garrison's face with his move. Now again, I read all of this pretty neat definition, but I don't believe it. I don't care what anybody says."