As President Donald Trump continues to chastise NFL players who kneel in protest during the national anthem before games, some football fans are wondering: Does the NFL league rulebook require players to stand for the anthem? A viral Facebook post referencing section a62 63 of the rulebook claims it does.

Before we verify or debunk that claim, it’s important to know that NFL football games are governed by multiple codes of conduct. One is the NFL rulebook; another is the NFL game operations manual. The rulebook is concerned with in-game actions by players and coaches (like scoring, penalties, challenges and so on), whereas the game-operations manual dictates how NFL games should be run in the bigger-picture organizational sense.

“The league’s Game Operations Department uses the manual to govern the conduct of home clubs, to ensure they protect players and provide the conditions for a fair and fan-friendly contest,” reads the NFL’s website. “Clubs face warnings and other penalties for noncompliance.”

The NFL rulebook makes no mention of the national anthem. But the game operations manual does.

Here’s what the game operations manual says regarding the national anthem, according to an NFL spokesperson:

The National Anthem must be played prior to every NFL game, and all players must be on the sideline for the National Anthem. During the National Anthem, players on the field and bench area should stand at attention, face the flag, hold helmets in their left hand, and refrain from talking. The home team should ensure that the American flag is in good condition. It should be pointed out to players and coaches that we continue to be judged by the public in this area of respect for the flag and our country. Failure to be on the field by the start of the National Anthem may result in discipline, such as fines, suspensions, and/or the forfeiture of draft choice(s) for violations of the above, including first offenses.

It’s important to note the use of the word “may” here. The NFL is not considering punishing fines on players or teams who choose to kneel or stay in the locker room during the national anthem, the spokesperson says.

— Sean Gregory contributed to this report.

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Write to Alex Fitzpatrick at alex.fitzpatrick@time.com.