NFL teams will be fined if players kneel for the US national anthem under a new policy.
The American football league said players who do not stand for the Star-Spangled Banner can stay in the locker room until it has been performed.
The NFL also vowed to "impose appropriate discipline on league personnel who do not stand and show respect for the flag and the Anthem."
Players said the protests were against policy brutality of African Americans.
"It was unfortunate that on-field protests created a false perception among many that thousands of NFL players were unpatriotic," said NFL Commissioner Roger Goodell in a statement accompanying the policy change.
"This is not and was never the case. This season, all league and team personnel shall stand and show respect for the flag and the Anthem.
"Personnel who choose not to stand for the Anthem may stay in the locker room until after the Anthem has been performed."
The new policy includes the provision that individual clubs can develop their own rules - that abide by the new principles - about how to handle personnel who do not wish to stand.
The NFL's policy statement said the move was meant to reaffirm a "strong commitment" to work with players "to strengthen our communities and advance social justice".