The NFL, the target of criticism from President Donald Trump over whether players should stand for the national anthem, is on strong legal ground if owners decide to unilaterally require players to stand, law experts said.

It’s unclear that’s where the league is headed. Owners meet this week, and in a rare move invited NFLPA leadership to the gathering, a sign they may want to avoid any decree from above on the issue. But if compromise fails with the players, the NFL could require standing.

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“In states like California, the free speech provisions of the [state] constitution have been deemed applicable to private sector employees,” said Bill Gould, a Stanford Law School professor and one-time chairman of the National Labor Relations Board.

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Owners might be able to make a legal case, he added, if they can prove that, by kneeling, players are harming the sport’s economic interests. He pointed to the arbitration case of former pitcher John Rocker, whom MLB suspended in 2000 after he made derogatory comments about minorities in an interview. An arbitrator reduced the suspension in part because MLB did not make a case that its economic interests were hurt by the free speech exercised by Rocker, Gould said.