The world's biggest social networking site Facebook has tightened its rules on posts relating to guns.
The site said it will remove posts from users who "indicate a willingness" to break the law - like requiring no background check - to sell firearms.
Access to posts related to sale of guns and other regulated items will be restricted to users over the age of 18.
Facebook has been under pressure from lobbying groups to alter its policy on such posts.
While the website is not an e-commerce platform, people use it to promote their goods and solicit buyers.
"People sometimes use our free tools to discuss products that are regulated or controversial," the firm said in a blog post.
"It is one of many areas where we face a difficult challenge balancing individuals' desire to express themselves on our services, and recognizing that this speech may have consequences elsewhere."
The firm said that it had worked with various stakeholders, including New York Attorney General Eric Schneiderman, to develop the new rules.
Under the guidelines, private sellers of firearms in the US will not be permitted to specify "no background check required", nor can they offer to transact across state lines "without a licensed firearms dealer".
The new regulations, which will be enforced in the coming weeks, will also apply to its photo sharing site Instagram.