Amazon has sent a warning to merchants about the potential consequences of congressional antitrust legislation.

Amazon is expressing concerns about a slew of bills making their way through Congress, telling a group of firms who sell on Amazon’s marketplace that the proposed legislation might harm them. According to CNBC, the firms were advised to contact Amazon policy specialists to learn more.

“We are concerned that they could potentially have significant negative effects on small and medium-sized businesses like yours that sell in our store,” the company reportedly said in the emails.

The emails come as big technology companies face increasing antitrust regulation on many fronts, including antitrust legislation sponsored by a bipartisan group of legislators. Two of the measures may have a direct impact on Amazon’s connection with third-party sellers by prohibiting them from compelling merchants to purchase Amazon items to enhance search results or get access to the company’s marketplace.

Furthermore, the US Federal Trade Commission is currently led by Lina Khan, an antitrust reformer who has written extensively on how antitrust rules should be applied more liberally to the IT sector. Khan has received requests from both Amazon and Facebook.