NFL owners have decided to fine teams if players refuse to stand for the national anthem.
The new policy announced on Wednesday came after President Trump lashed out at NFL players who protested against racial injustice by kneeling during pre-match ceremonies.
The movement began two years ago when San Francisco 49ers quarterback Colin Kaepernick kneeled in protest against police shootings of unarmed black men.
Players, however, will be allowed to stay in the locker room during the "The Star-Spangled Banner" if they refuse to comply with the new policy.
The NFL Players Association criticized the move, saying it wasn't consulted and would challenge any changes that violate the collective bargaining agreement.