Editor's note: This story has been updated since it was first published in September.
The NFL's approval of a new national anthem policy has sparked renewed interest about how it's observed at sporting events.
How do other policies compare to the NFL's mandate for players who are on the field to stand? An ESPN review of seven leagues and the NCAA reveals few official requirements.
Owners adopted a new policy that requires all players and team personnel to "stand and show respect for the flag and the anthem" if they are on the field during the performance. Players, however, have the option of going to the locker room during the anthem if they don't "feel that's within the way they feel about the particular subjects," in the words of Pittsburgh Steelers owner Art Rooney II.
Discipline is complicated. The league will fine the team of any player who protests, but each team can develop its own internal policy for disciplining players. Some owners, including the New York Jets' Christopher Johnson, do not plan to punish players who protest. So it will be possible for a player to protest without incurring individual discipline.
The league did not say how it will define what it means to protest, other than to say it will know it when it sees it.
The six pillars of the rule are:
All team and league personnel on the field shall stand and show respect for the flag and the anthem.
The Game Operations Manual will be revised to remove the requirement that all players be on the field for the anthem.
Personnel who choose not to stand for the anthem may stay in the locker room or in a similar location off the field until after the anthem has been performed.
A club will be fined by the league if its personnel are on the field and do not stand and show respect for the flag and the anthem.
Each club may develop its own work rules, consistent with the above principles, regarding its personnel who do not stand and show respect for the flag and the anthem.
The commissioner will impose appropriate discipline on league personnel who do not stand and show respect for the flag and the anthem.
NBA and WNBA
Rules for both leagues are identical in this regard: "Players, coaches and trainers are to stand and line up in a dignified posture along the sidelines or on the foul line during the playing of the national anthem."
In September, NBA commissioner Adam Silver said he expected players to stand, but stopped short of making it a requirement. "It's my hope that our players will continue to use that as a moment of unity," Silver said.
There is no mention of discipline, but Silver also added that if a player were to not stand for the anthem that the league would "deal with it when it happens."
The entire Indiana Fever team and two Phoenix Mercury players were not penalized for kneeling during the anthem before a WNBA playoff game in September 2016. Meanwhile, the NBA did set a precedent when Denver Nuggets guard Mahmoud Abdul-Rauf decided not to stand during the anthem late in the 1994-95 season. He believed the anthem and flag were not inclusive, either religiously or politically.
Abdul-Rauf's position went unnoticed for months and when it became public the following season, the NBA told him he could remain in the locker room if he did not want to stand, but he refused, according to a report by Outside the Lines. The league suspended him for one game without pay, a loss of $31,707. Afterward, he agreed to stand -- but pray -- during the anthem.
Major League Baseball
There are no documented rules on this issue, an MLB spokesperson said in September. The spokesman added: "While this is not a league rule, the playing of the national anthems of the United States and Canada remains an important tradition that has great meaning to our fans. The playing of 'God Bless America' at designated games is a club choice."
According to a league spokesperson, the only formal rule regarding the anthem is that it must be played before games, be it the U.S. or Canadian version or both, depending on the teams involved. There is no mention of being on the ice or standing during the performance.
NHL Players' Association executive director Don Fehr said in a statement in September that any NHL player would have the union's "full support" if he chooses to make a "peaceful protest."
NASCAR has no written policy about the national anthem and took no stance on the issue when it released this statement in September: "Sports are a unifying influence in our society, bringing people of differing backgrounds and beliefs together. Our respect for the national anthem has always been a hallmark of our pre-race events. Thanks to the sacrifices of many, we live in a country of unparalleled freedoms and countless liberties, including the right to peacefully express one's opinion."
Despite NASCAR having no stance, President Donald Trump praised it in regards to the anthem when he welcomed 2017 NASCAR Cup Series champion Martin Truex Jr. to the White House on Monday.
"I will tell you, one thing I know about NASCAR, they do indeed, [NASCAR chairman] Brian [France], stand for the playing of the national anthem, right? They do indeed," Trump said.
Drivers and team personnel typically line up either by their car or pit stall during the anthem; the drivers then get five minutes to get into the car before the engines are fired.
There are no bylaws pertaining to the national anthem, according to NCAA associate director of public and media relations Gail Dent. Dent added that student-athletes are expected to follow sport-specific tournament policies when asked about the issue on Wednesday.
U.S. Soccer Federation
Last May, the group that governs the U.S. men's and women's national programs enacted one of the strictest rules ESPN could find. It reads: "All persons representing a Federation national team shall stand respectfully during the playing of national anthems at any event in which the Federation is represented."
The rule came after Megan Rapinoe, a member of the U.S. women's team, knelt prior to a game against Thailand in September 2016.
Major League Soccer
The league encourages players to stand but will not require them to do so.
In a statement released in September, the MLS said: "The march of players, officials and children into our stadiums and singing of the anthem has been a pre-match tradition since our first game in 1996. The National Anthem provides our clubs and fans an important and time-honored opportunity to salute our country and stand up for its principles -- whether in the United States or in Canada.
"At the same time, freedom of speech -- and the right to peaceful protest -- are the hallmarks of both countries. Though we encourage our players to stand during the national anthem, we respect and support their right to express their personal beliefs."
ESPN's Jerry Crasnick, Melanie Jackson, Emily Kaplan, Bob Pockrass, Mitch Sherman and Ohm Youngmisuk contributed to this report.