The CEO of Birkenstock is waging a war against Amazon.

David Kahan sent a brutal five-page email to sellers of Birkenstocks last week that accused Amazon of launching an "assault on decency" and warned retailers against selling even a single pair of shoes to the ecommerce giant, The Washington Post reports.

"This is a personal note sharing a situation that I personally find sickening and professionally will not tolerate," Kahan wrote in the email, according to a copy that was shared by The Post.

Birkenstock retailers are already prohibited from selling to Amazon.

Kahan implemented a ban on selling Birkenstocks to Amazon last year, citing issues with counterfeit products.

Amazon is now trying to circumvent that ban by contacting retailers directly and asking them to sell their products to Amazon regardless, according to Kahan. 

"Quite frankly I see this action by Amazon as pathetic," Kahan wrote. "Amazon can't get Birkenstock by legitimate means so why not dangle a carrot in front of retailers who can make a quick buck."

He said retailers will be closed "FOREVER" if they sell a single pair of shoes to Amazon.

"This is a middle finger to all brands, not just Birkenstock," Kahan told The Post in an interview.

A spokeswoman for Amazon declined to comment on Kahan's complaint when reached by The Post. Amazon did not immediately respond to Business Insider's request for comment.

ncG1vNJzZmivp6x7o8HSoqWeq6Oeu7S1w56pZ5ufonyjtdGknKerpKSwrHnCnqZmpJGotaa%2FjKisrWWRqXqiucCzpqdlmaN6o77UrZilZZyawbWx0WZpaWlnYoQ%3D