The Sioux tribe of North America is demanding that the famous Parisian nightclub The Crazy Horse change its name out of respect for a former chief.
Alfred Red Cloud: Name Crazy Horse "is sacred"
Harvey White Woman, a descendant of Crazy Horse, told the club that "my family are offended whenever there is a show of disrespect to our culture".
The letter was delivered to the club by Alfred Red Cloud, 53, on behalf of the Oglala Sioux from South Dakota.
Crazy Horse spearheaded resistance to the US military in the 19th Century.
Mr White Woman said the letter was prompted by the discovery that stage shows at the Crazy Horse featured pseudo-Indian feathered headdresses - on mostly naked dancers.
"I want the young people of my tribe to remember him as a strong leader and warrior and not some nightclub in Paris," he added.
The famous Crazy Horse club was founded in 1951
Red Cloud said the letter did not threaten legal action, but he warned that relatives of Crazy Horse were prepared to do "whatever it takes" to get the name changed.
The club said it has no wish "to make this demand a public affair" and "reserves the right to respond directly to Mr Harvey White Woman".
Mr White Woman, of the Pine Ridge Indian Reservation, is an executor of the estate of Crazy Horse.
Crazy Horse, or Tashunka Witko, was born in South Dakota in the early 1840s, and was revered by his people after his death in 1877 for leading the fight against the US military.
The Sioux resisted the military's campaigns to drive them out of the mineral-rich Black Hills and onto reservations.
Crazy Horse was finally arrested by US forces and stabbed to death during an escape attempt.
The club's website says its founder, Alain Bernardin, "was fascinated by the America of the cowboy saloons and the myth of the Far West".