The NFL’s Miami Dolphins are threatening to suspend players who protest during the national anthem for up to four games.

The policy was announced in a recently issued nine-page discipline document under the section “Proper Anthem Conduct.”

So far, NFL players have not reacted well to the league’s mandate that they stand at attention during the national anthem in the upcoming season. The NFL Players Association has threatened to take the league to court if it attempts to fine teams, as promised. The two sides will meet with an independent arbiter later this month.

But this latest report is the first to surface regarding individual team discipline.

The Miami Dolphins document lists anthem protests under “conduct detrimental to the team,” and mentions suspensions, fines or a combination of both as a possible penalty.

So far, at least one NFL star is thumbing his nose at the league’s new rules regarding protests during the national anthem. “I’m going to take a fine this year, why not?” Tennessee Titans defensive end Jurrell Casey told CNN earlier this month.

“I’m going to protest during the flag — that’s what I’m going to say now,” Casey told the cable news outlet during a promotional event in London.

Casey, who has gone to the NFL’s Pro Bowl three consecutive years, is the most prominent player to state publicly that he will ignore the new guidelines, which gives players the option to remain in the locker room if they don’t want to stand for “The Star-Spangled Banner.”

Others have grumbled in the press about the new league mandate. Training camps starts in about a week for most teams, with the regular season about six weeks away.

Last year, the Dolphins had three players protest the anthem by kneeling, raising a fist, or staying in the locker room. Wide receiver Kenny Stills, safety Michael Thomas, and tight end Julius Thomas knelt during the anthem. Only Stills is with the team, as Michael Thomas has signed with the New York Giants and Julius Thomas was released.

Miami Dolphins owner Steve Ross was one of the most outspoken executives against anthem protests last season.