The alleged problem? Beckham was showing a little too much skin during last week’s game against the Seattle Seahawks.
In a letter from the league that he later posted to his Instagram on Monday, Beckham revealed he was fined more than $14,000 after officials found him to be in “violation of the NFL Uniform and Equipment Rules” during an Oct. 13 game against the Seahawks.
“Specifically, your pants failed to cover the knee area,” the letter went on to say.
The 26-year-old wide receiver, who previously played five seasons with the New York Giants before being traded this offseason, called the fine “ridiculous.”
“14K for some pants that are NOT gonna protect me from anything…this shxt is ridiculous,” Beckham wrote.
This isn’t the first time the league has taken issue with Beckham’s uniform this season.
Beckham was memorably reprimanded for wearing a nearly $200,000 watch during the Browns' opener, and said it was only an issue because he was the one with it on. The following week, he was sent off the field by officials during a game in New York because they said his helmet visor was too dark.
"It's crazy," he said at the time, unaware of his impending uniform violation fine.
"The NFL finds ways to just take [money]. They're going to take it from you. I understand a penalty, getting fined for that. But pants above the knees, a shirt hanging out, and you're getting $5,000 taken from you? Pads above your knees? You really think that this little knee pad covering my kneecap is going to affect, if somebody hits me, weighs 250 pounds, running 18 mph?”
He continued: "I don't do physics, but if I get hit, this is not going to protect me.”
Beckham was also fined an undisclosed amount by the league after getting into a spat with Baltimore Ravens cornerback Marlon Humphrey on Sept. 29.
Humphrey appeared to choke Beckham after throwing him to the ground during the fight, although both players denied starting the altercation.
Beckham will likely have to pay at least $70,000 — the league's standard penalty for a second fight. He was suspended one game for a helmet-to-helmet hit on Carolina's Josh Norman in 2015, and had been fined more than $220,000 before his altercation with Humphrey.
Beckham will likely appeal Monday’s fine.
The Associated Press contributed to this report.