President Donald Trump is continuing his attack against NFL players and other athletes who kneel in protest during the national anthem, saying such actions are disrespectful of “our country, flag and national anthem.”
Whether players’ pregame protests are disrespectful, a form of free speech, or somewhere in between is a matter of debate. But the dispute has raised an important question: What are the rules regarding how Americans should treat the U.S. flag?
The United States Code, a collection of all federal laws in the U.S., has a section dedicated to the flag — Title 4, Chapter 1 — sometimes called the “Flag Code.” The Flag Code covers how the flag should be designed, whether it should be used in advertising, and how it ought to be displayed, among other subjects. The President has the power to change the Flag Code unilaterally at any time.
Penalties for violating the Flag Code are not enforced; the Supreme Court has found it unconstitutional to prohibit desecrating the flag. Instead, the Flag Code can be considered a list of guidelines for proper conduct regarding the flag.
As the sports world’s debate over national anthem protests rages on, here are several ways in which people commonly violate the Flag Code.
Using the flag on athletic uniforms
Teams in the NFL and other leagues often wear and sell jerseys or other athletic gear featuring the U.S. flag. But as the Flag Code states: “No part of the flag should ever be used as a costume or athletic uniform. However, a flag patch may be affixed to the uniform of military personnel, firemen, policemen, and members of patriotic organizations. The flag represents a living country and is itself considered a living thing. Therefore, the lapel flag pin being a replica, should be worn on the left lapel near the heart.”
Carrying the flag horizontally
During many pregame national anthem ceremonies, a flag is brought out and held over the field. However, the Flag Code says that “the flag should never be carried flat or horizontally, but always aloft and free.”
Letting the flag touch the ground
Flags often adorn football fields and other playing surfaces. But as the Flag Code states, “The flag should never touch anything beneath it, such as the ground, the floor, water, or merchandise.”
This story originally appeared on TIME.com.