When police in the small Utah state town of Roosevelt saw a Maori haka being performed after a high school game of American football, they thought a riot was breaking out and used pepper spray and batons on the spectators involved.
An investigation by police in Roosevelt, 140 miles east of Salt Lake City, has cleared the officers of wrongdoing "because they feared a riot".
A spokesman from the American Civil Liberties Union has said the decision to interrupt a cultural ritual may have violated constitutional rights.
The traditional Maori challenge has been adopted by several US sports teams, especially those with Polynesian players.
Union High School fans, having watched their team slump to another defeat, decided to perform a haka to raise their spirits.
Police officer Wade Butterfield, who baton charged the group, said: "I have seen a riot first-hand and know how dangerous they can be."
Roosevelt police said officers will be given additional training in cultural diversity and customs.