Birkenstock has a message for customers shopping on wife shared video sexAmazon: "BUYER BEWARE."

Fed up with counterfeit products and unauthorized sellers, the iconic sandal retailer is planning to remove its merchandise from the e-commerce giant beginning January 1, 2017.

Birkenstock USA CEO David Kahan announced the decision — with that all-caps warning — in a July 5 memo to retail partners, as reported by CNBC. A spokesman for Birkenstock USA confirmed that report.

"The Amazon marketplace, which operates as an 'open market,' creates an environment where we experience unacceptable business practices which we believe jeopardize our brand," Kahan wrote. "Policing this activity internally and in partnership with Amazon.com has proven impossible."

The retailer won't authorize third-party sellers or sell to Amazon via a third party, either.

Birkenstock will tell customers that they should "only purchase Birkenstock products from authorized retailers," Kahan wrote in his letter.

"If they see any Birkenstock product on Amazon.com, we cannot in any way confirm its validity or verify its quality. It may be counterfeit. It may be stolen. It may be manufactured under questionable labor and environmental conditions," Kahan wrote.

Birkenstock is one of several companies that have been plagued by Chinese knock-offs online. Many Amazon listings of the brand's sandals are priced $20 below the traditional retail price.

Other companies have sparred with Amazon over third-party sellers. In 2013, Johnson & Johnson stopped selling some of its products through the site over a similar complaint. Smaller companies, too, like the German chef knife maker Wüsthof have protested Amazon's reluctance to intervene over discounted third-party products.

Birkenstocks will still be available online from the brand's official website, even if they're not eligible for Amazon Prime.

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