Urban Outfitters' line of Navajo-branded clothing and accessories has set off a firestorm online and within the Navajo Nation government, with allegations of trademark violations and criticism of the products -- particularly underwear and a liquor flask -- that many tribal members consider disrespectful.

Native American-inspired prints have shown up on runways for years, and it's common for designers to borrow from other cultures.

But the Navajo government's issue with Urban Outfitters is the clothing chain's use of the name "Navajo" on its products and in marketing. The tribe holds at least 10 trademarks on the name that cover clothing, footwear, online retail sales, household products and textiles.

The tribe's Department of Justice sent Urban Outfitters CEO Glen Senk a cease-and-desist letter in June, demanding that the company pull the Navajo name from its products. The tribe has received no response but says it remains "cautiously optimistic" it can persuade Urban Outfitters to adopt another name and trademark.

"When products that have absolutely no connection to the Navajo Nation, its entities, its people, and their products are marketed and retailed under the guise that they are Navajo in origin, the Navajo Nation does not regard this as benign or trivial," said Brian Lewis, an attorney for the tribe. "It takes appropriate action to maintain distinctiveness and clarity of valid name association in the market and society."

Urban Outfitters, which has stores across the country and overseas, said it has not heard from the Navajo Nation and has no plans to alter its products.

"Like many other fashion brands, we interpret trends and will continue to do so for years to come," company spokesman Ed Looram said. "The Native American-inspired trend and specifically the term `Navajo' have been cycling through fashion, fine art and design for the last few years."

While the Navajo Nation has not threatened legal action, law professor Bill Hennessey thinks it has a strong case. He said the tribe could argue the products cause confusion among customers about who manufactured them.

Hennessey points specifically to a trademark governing textiles that was registered to a Navajo Nation enterprise in 2008.

"If you're going to maintain control over your mark, the more quickly you bring an action against the infringer, the more likely the federal court is going to grant an injunction order prohibiting Urban Outfitters from continuing to use the word `Navajo,"' said Hennessey, who teaches at the University of New Hampshire's Franklin Pierce Center for Intellectual Property.

Urban Outfitters labels more than 20 products on its website with the word "Navajo," including jackets, earrings, scarves and sneakers. But the two items that have sparked possibly the most controversy online are the "Navajo Hipster Panty," and the "Navajo Print Fabric Wrapped Flask." Both have geometric designs common in Navajo arts and crafts.

Dwayne Clauschee, a designer from the Navajo town of Chinle in Arizona, said Urban Outfitters and other clothing companies are trying to cash in on a trend he believes has been done more respectfully and tastefully in higher-end fashion.

A "Navajo" flask is "extremely insensitive" considering the long history of alcohol abuse among Native tribes, many of which ban the sale and consumption of alcohol on their reservations, he said. The Navajo Nation is among them. And branding underwear as "Navajo" goes against the tribe's spiritual beliefs of modesty and avoidance of indecency, Clauschee said.

Jessica Metcalfe, a Turtle Mountain Chippewa from North Dakota who writes a Native American fashion blog, tells Urban Outfitters to knock it off. "Don't claim Navajo, unless it's Navajo, and you ain't Navajo."

Sasha Houston Brown of the Santee Sioux Nation posted a letter online to the company saying it "has taken Indigenous life ways and artistic expressions and trivialized and sexualized them for the sake of corporate profit."

Urban Outfitters isn't alone in its Navajo-branding.

Fermin Navar and his business partner, Phil Brader, signed a 75-year licensing agreement with the Navajo Nation in 2007 that allows them to sell skin care products and clothing under the Navajo name in exchange for a share of the profits. Navar said they've come up with a list of nearly two dozen companies they believe are violating the trademark.

The name appealed to Navar because the tribe is well-known for its huge reservation that spans 27,000 square miles in Arizona, Mexico and Utah; its membership that ranks among the top two for American Indian tribes; and its cultural beliefs that tie beauty to harmony. Navajos also are known more broadly for using their language to develop a code that confounded the Japanese and helped win World War II.

"The design doesn't matter; it's the use of the name Navajo," said Navar of Austin, Texas. "They can say it looks like this, but if it has the name Navajo -- it's being branded and sold as Navajo -- it's a violation."