Advocacy groups are raising objections and have filed a legal brief to revoke the Facebook "Sponsored Stories" settlement.

The social network introduced Sponsored Stories in 2011. The ad unit of Facebook did not go as expected by the company and was hit by a class action lawsuit. Filed court documents revealed that Facebook's Sponsored Stories violated user rights and privacy as it publicizes a user's online behavior and Likes without giving them the option to opt out of the service.

"Sponsored stories are messages coming from friends about them engaging with a Page, app or event that a business, organization or individual has paid to highlight so there's a better chance people see them," per Facebook.

Facebook also made a good profit with Sponsored Stories and according to the court document, the company generated more than $230 million from the service between January 2011 and August 2012.

In August of 2013, under terms of a settlement, Facebook paid $20 million in fines and charitable contributions. The company also agreed to amend its privacy policies and give more information about, and control over, how a user's name and photos are used in ads. The company also announced that it will bring down Sponsored Stories from April 2014.

However, on Thursday, February 13, non-profit advocacy group Public Citizen filed a legal brief, on behalf of five parents and their kids on Facebook, with the Ninth Circuit Court of Appeals of San Francisco, asking it to overturn the settlement. According to the original settlement, Facebook was asked to change the language of its terms of service to say that for people under the age of 18 years, the act of signing up for Facebook represents parental consent.

The advocacy group contends that the original settlement violates the laws of seven states, including California and New York, which require Facebook to receive explicit permission from parents before using personal information of teenage users in advertising.

"The default should be that a minor's image should not be used for advertising unless the parent opts in. Putting the burden on the parent to opt the child out gets it exactly backward," said Scott Michelman, a lawyer at Public Citizen.

Child advocacy group Campaign for a Commercial-Free Childhood also says that that the original settlement offers little protection to children. The group was supposed to receive about $290,000 under the settlement but now plans to ask the appeals court to reject it.