Birkenstock is pressuring retailers to stop selling similar styles from other brands, according to The Wall Street Journal.

Nordstrom and Zappos are among those that have reportedly stopped carrying some styles from Mephisto, Naot, Freedom Moses, and Viking Sandals.

“This is competitive bullying,” Rusty Hall, chief executive of Mephisto USA, told the WSJ. “We haven’t infringed on any design patent.”

A Birkenstock spokesperson told the WSJ that Birkenstock has an obligation to protect its brand and limit availability to retailers who maintain the brand’s integrity. The spokesperson also said retailers are making decisions on what to sell on their own.

Photo courtesy Birkenstock, Brooklyn