More than 94,000 people have signed an online petition calling on Facebook Inc. (NASDAQ:FB) to ban the sale and trade of firearms on the world’s largest social network.

Shannon Watts of Zionsville, Ind., who launched the petition, says Facebook and the Facebook-owned Instagram are being used to facilitate illegal gun sales among private sellers, often with zero oversight. Community pages and groups like “Guns for Sale” (208,000 likes) and “Colorado Gun Trader” (3,559 members) proliferate on Facebook, and Watts and other critics say they make it easy to obtain firearms without background checks.

“I think of Facebook and Instagram as places to share photos of my kids and family,” Watts writes in the petition, “not as an online market for guns.”

Shortly after the Dec. 14, 2012, massacre at Sandy Hook Elementary School in Newtown, Conn., Watts started a group called Moms Demand Action for Gun Sense in America, which aims to build support for “common-sense gun reforms.” The group was inspired in part by Mothers Against Drunk Driving, which for decades has advocated for stricter policies related to alcohol and driving.

Laws governing the sale of firearms vary greatly from state to state. The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives does not explicitly prohibit online gun sales, but generally speaking, a firearm “may not lawfully be sold by a licensed dealer to a non-licensee who resides in a state other than the state in which the seller’s licensed premises is located.”

Facebook, for its part, prohibits ads that promote firearms or ammunition, but it offers little guidance to users who buy and sell items independently on the site. The site considers any unlawful activity a violation of its terms, but critics say enforcement is difficult. Illegal gun sales have long plagued the likes of Craigslist and other online marketplaces.

In asking Facebook to crack down, Watts is joined by the group Mayors Against Illegal Guns, which in September estimated that as many as 25,000 guns a year are being illegally transferred via the Internet to people with criminal records.

“As moms, we’re among Facebook's largest and most loyal audiences,” Watts writes. “We need to tell Facebook loud and clear that allowing gun sales and trades -- which could easily put firearms in the hands of criminals and dangerous people -- is a threat to public safety and the security of our families.”

Watts’ petition is seeking 150,000 signatures and is targeting Mark Zuckerberg and Kevin Systrom, the chief executives of Facebook and Instagram, respectively. Read the full petition here.

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