Jacquelyn Martin/Associated Press

The president is a fan of the NFL's new national anthem rules, which require players on the field to stand during the song prior to games in the 2018 season.

As Fox & Friends shared on Twitter, Donald Trump said of the rule changes: "You have to stand proudly for the national anthem. You shouldn't be playing, you shouldn't be there. Maybe they shouldn't be in the country...the NFL owners did the right thing."

Ian Rapoport of NFL Network shared the league's new anthem policy, which notes "all team and league personnel on the field shall stand and show respect for the flag and the anthem" and that teams will be fined if players protest during the song.

The ruling also states players have the option to remain in the locker room if they do not want to stand:

Trump had tweeted about player protests during the anthem a number of times during the 2017 season. In one message in September, he suggested the league change its policy: "Sports fans should never condone players that do not stand proud for their National Anthem or their Country. NFL should change policy!"

That tweet followed comments Trump made at a rally that month, where he said NFL owners should "get that son of a b---h off the field right now" if a player knelt during the anthem.

Vice President Mike Pence already reacted to the rule changes on Twitter, using the hashtag #Winning:

Pence left a game he attended between the San Francisco 49ers and Indianapolis Colts in October because some players didn't stand for the anthem.

After the policy was announced Wednesday, the NFL Players Association said it would challenge the ruling, describing it as "inconsistent with the collective bargaining agreement":

According to Bleacher Report's Mike Freeman, "an intense fear of Donald Trump" motivated this new policy, with one team official saying the league "is f--king terrified of Trump."

Jim Trotter of NFL media reported some players felt the rules were changed out of fear and the desire to not have Trump use protests as a talking point before midterm elections.

Philadelphia Eagles defensive end Chris Long tweeted "this is fear of a diminished bottom line" and "fear of a president turning his base against a corporation":

Don't expect the rule changes to make this a non-issue, though. Robert Klemko of Sports Illustrated said some players who weren't even planning on demonstrating during the anthem are discussing doing so in 2018 in ways that would "skirt" the new policy "just to spite the NFL."

Former 49ers quarterback Colin Kaepernick first started protesting during the national anthem in the 2016 preseason as a means of protesting racial injustice and police brutality. Others started doing so as well across the NFL and in other sports.

Following Trump's September comments ahead of Week 3 in the NFL's 2017 season, many teams and players protested during the anthem or before their games.

Kaepernick wasn't signed during the 2017 campaign despite having a Super Bowl appearance on his resume and a solid 2016 campaign in which he threw 16 touchdowns to just four interceptions as the 49ers' starter. He filed a grievance against the league and its owners alleging they colluded to keep him out after his protests.