A statement from NFL Commissioner Roger Goodell regarding the new decision reads in part: "This season, all league and team personnel shall stand and show respect for the flag and the anthem".
Trump has been critical of the protests since they began during the 2016 preseason, when then-San Francisco 49ers quarterback Colin Kaepernick raised eyebrows - and some rankles - by taking a knee during the pregame playing of "The Star-Spangled Banner".
President Trump, in an exclusive interview with Fox News, said he believes NFL owners "did the right thing" by instituting a new policy mandating players and personnel stand for the national anthem or face a fine.
One organization, the National Action Network, will march on league headquarters Friday to "advocate for players' right to kneel and call on NFL owners to reverse (the) risky decision violating players' First Amendment rights by imposing fines for not standing during the national anthem". "Maybe you shouldn't be in the country", Trump said. The owner of the New York Jets also took a more conciliatory approach, promising not to punish any player who continues to protest against social injustice in full view of fans. Or you shouldn't be playing, you shouldn't be there. The players not on board will have to stay in the locker room.
Marcio Jose Sanchez AP FILE
For tactical reasons, I'm not a big fan of kneeling during the national anthem as a form of protest. Any violations of the new rules would result in fines against teams.
Finally, an attempt to bring this to the National Labor Relations Board (NLRB) might fail if the dispute is deemed to arise over a societal protest rather than working conditions, though it could be argued that now the dispute is about work rules and the NLRB has viewed worker free speech to be protected. "I think it's the right thing to do".
The players' union said it wasn't consulted in the talks and would file a grievance against any change in the collective bargaining agreement.
Democratic U.S. Senator Ben Cardin said the Republican president's words were "inflammatory", but not unexpected, and added that Trump's suggestion that players should be ousted is "never going to be acceptable to me and, I think, to many Americans".