Dave Kahan, CEO of Birkenstock, in an e-mail to his retail partners called Amazon’s new third-party inventory purchasing program an “assault on decency” because it’s allegedly aimed at selling products not currently approved for the online retail site, according to a report on CNBC.

According to the e-mail received by the Washington Post, Kahan called the program a “pathetic” attempt by Amazon to create a backchannel means to sell products not offered on its site.

Kahan also warned his sellers: “Any Authorized retailer who may do this for even a single pair will be closed FOREVER. I repeat, FOREVER.”

Many retailers of Birkenstock who are not authorized to resell on Amazon received the e-mail announcing the program from Amazon. Amazon has indicated that the program will provide Amazon with larger inventory access to meet customer’s needs but some see the program also providing access to brands that refuse to sell on Amazon’s platform.

Photo courtesy Birkenstock