Houston Texans players kneel during the singing of the national anthem before an NFL football game against the Seattle Seahawks, Sunday, Oct. 29, 2017, in Seattle. (AP Photo/Elaine Thompson)

State constitutions each contain clauses on protecting free speech. Many argue that Trump’s public communications to NFL executives to stop the protests of NFL players is a clear suppression of free speech.

Also, transcripts from NFL meetings and depositions taken in Colin Kaepernick‘s collusion case also showed that the NFL approved the policy to “restrict the political content of players’ protests merely out of fear of how fans—or the president—will respond,” Slate’s Nikolas Bowie wrote. Constitutions in certain states—including California and New Jersey —prohibit private institutions from fining protesters or subjecting them to “unreasonably restrictive or oppressive conduct.” Thus, the transcripts and depositions demonstrate that the NFL’s policy likely violates several state constitutions.

Players could be allowed to continue kneeling in states with constitutions containing provisions broad enough to stop the NFL from restricting protests. Though it would require a legal challenge, traditionally, state supreme courts have been “more willing than the U.S. Supreme Court to subject organizations like the NFL to the same constitutional standards as governments,” Bowie wrote.

As national discussions about the protests begin to include state constitution provisions, some players are finding ways to protest off the field. Philadelphia Eagles safety Malcolm Jenkins held a silent protest in his team’s locker room Wednesday in which he held up signs about mass incarceration and the fatal police shootings of people of color.