The most popular mixed martial arts organization in the United States is laying down the law: You can fight with us, you can bleed for us, you can shout till you're hoarse for us ... but under no circumstances can you walk into an eight-sided ring looking like a Nazi.

Zuffa LLC, which owns World Extreme Cagefighting and the Ultimate Fighting Champioship, is standing by its decision to ban apparel made by Hoelzer Reich, a California apparel company, due to the "offensive" images on the clothing that invoke symbols of Nazi Germany.

World Extreme Cagefighting general manager Reed Harris told FoxNews.com the decision was a "no-brainer" after a Dec. 5 bout in which UFC fighter Joe Brammer wore a Hoelzer Reich shirt featuring an iron cross.

"We felt there was a possibility that some of their clothing, some of their symbols could be offensive," Harris said. "Once we looked into it, we immediately made the decision to not allow them into our events. It was a no-brainer, it really was."

The "shocking" images found on some Hoelzer Reich apparel, Harris said, will be permanently banned from all WEC and UFC fights.

Jamie Vine, owner of Hoelzer Reich, has apologized for "any controversy and the excessive media attention it has brought to Zuffa," but she defended the symbols on the clothing, saying they predate the Third Reich by centuries.

"The imagery that we reference dates back hundreds of years before Nazi Germany, and we did not realize that the brief association some of the imagery had with Nazi Germany over 70 years ago would still be so sensitive to so many people," the company said in statement issued earlier this month.

"Bottom line: we NEVER meant to offend ANYONE. We do not support the Neo Nazi 'cause,' nor do we promote any racist ideologies."

Other images found on Hoelzer Reich apparel include depictions of the Prussian/German war helmet and flaming skulls surrounding the iron cross.

Vine said she was "not at all surprised" by the controversy surrounding her company's apparel, but she was adamant that Hoelzer Reich garments do not contain images of swastikas or SS bolts.

"It's about family history," she told FoxNews.com. "It's not about Nazis at all."

She declined to indicate whether the shirt Brammer wore into the ring will be discontinued.

According to its Web site, Hoelzer Reich translates directly to "Lumberjack Nation" or "Lumberjack Empire."

"We chose the name Hoelzer Reich, not only because it reflects Strength and Honor, but because it is part of our family history," the Web site reads. "We do not have any Political affiliations with any organizations, nor specific views of any controversial parties. Our interest in the Iron Cross and German history comes strictly from a historical and ancestral standpoint."

Calls to Brammer seeking comment were not returned Tuesday.

Ardy Arani, managing director and CEO of Championship Group Inc., a sports marketing firm based in Atlanta, said the move by Zuffa to ban the controversial apparel is proof that the company is serious about regulation.

"The UFC is attempting to regulate themselves like any other legitimate sport does," Arnai told FoxNews.com. "What this points out if they're serious about it. They're saying, 'Hey guys, we're running a sport here. We get to write the rulebook.'"

Rick Burton, a sports marketing professor at Syracuse University and former chief marketing officer of the United States Olympic Committee, said Zuffa was right to ban the clothing.

"These are some of the most offensive images in history," Burton said. "So I think the organization is obviously not wanting that association with their product and with their brand."