Facebook may have agreed to pay $5 billion this week to settle a case with the federal government about how the company has protected its users data, but that doesn’t mean the feds are done with the social-media giant.

Facebook co-founder Chris Hughes is reportedly working with federal regulators, and a pair of prominent antitrust academics, to build a case for the government breaking up the company that he started when he and company Chief Executive Mark Zuckerberg were students at Harvard University. The New York Times and the Washington Post both reported on Hughes’ involvement in the effort to force Facebook to either split up, or divest itself of properties that have increased the company’s dominance in the social networking industry and given in access to the personal data of billions of individuals around the world.

The Times reported that Hughes has been working with Scott Hemphill, of New York University, and Tim Wu of Columbia University, and meeting members of the Federal Trade Commission, the Justice Department and some states attorneys general, on build a case for the U.S. government to seek the breakup of Facebook on antitrust grounds. Among the examples being cited of Facebook’s alleged unfair market dominance are the company’s $1 billion acquisition of Instagram, in 2012, and its 2014 purchase of messaging app company WhatsApp, for $19 billion.

While Hughes has been involved in presentations made to the federal officials, the degree of his involvement remains in question. According to the Times, Hemphill would only say that Hughes “has been an important contributor to thinking about these issues.”

Hughes hasn’t worked at Facebook since he left the company in 2007 and cashed out his stock holdings worth approximately $500 million. However, his role as a Facebook co-founder, and his calls for Facebook to be broken apart, have added ammunition to other efforts to rein in the company, and power of CEO Zuckerberg.

In May, Hughes published a lengthy editorial piece in the New York Times saying, among other things, that the government needs to step in a split up Facebook, and that Zuckerberg’s 60-percent share of Facebook’s voting shares give him a degree of corporate and societal power that is “unprecedented and un-American” in nature.

Facebook didn’t immediately respond to a request for comment on Hughes.