LAS VEGAS — At 11:47 p.m. Eastern on Sunday, in a sport that legalizes the helmet-to-helmet collision of two men moving at highway speed, the National Football League reached a consensus about bodily fluids.

The consensus arrived on the field, in the form of a flag.

Buffalo Bills safety C.J. Gardner-Johnson was disqualified from the Raiders game just before halftime for spitting toward Las Vegas tight end Brock Bowers and a group of Raiders players. The Bills won 33-30. The spit, by any measure, was the more consequential act.

I. The Act

The clip, which the NFL on CBS posted and which has now been watched by every human being with a phone, shows Gardner-Johnson turn toward the Raiders group and deliver. Raiders center Tyler Linderbaum saw it, flagged it, and summoned the umpire, in a sequence broadcasters are already calling “the biological attack.”

II. The Flag

Unsportsmanlike conduct. In the National Football League, a player may lower a shoulder into a man’s chest, and the crowd cheers. A player may drive a helmet into a rib cage, and the league reviews the play for technique. A player may not spit. The drool is the red line.

III. The Broadcast

Nate Burleson and Bill Cowher, on the CBS desk, called it a dereliction of duty. They used the word “shameful,” a word that has been applied to many plays in this building, and now to one fluid.

IV. The Apology

Gardner-Johnson apologized on Monday, a statement that arrived with the speed of a man who has seen the clip.

V. The Precedent

The league has fined players for words, for gestures, for dancing, for the color of their socks. It has never, in this desk’s reading, legislated saliva. The rulebook is now one and a half pages longer.

"In a sport where a 280-pound man is legally allowed to use another man's head as a brake, the league drew the line at drool."

The physics of the act, as seen in the clip, are unremarkable: a small arc, a brief flight, a landing near the feet. The arc is the whole story. A 6-foot safety, 205 pounds, generated a projectile that a 6-foot-5 tight end identified in flight, and the identification — not the spit — is what ended the night.

At 11:52 p.m., the stadium lights were on, the scoreboard read 33-30, and the most disciplined league in the world had a new rule, written by a man with a mouth.