London (CNN Business) One day after a Facebook co-founder called for the company to be broken up, Mark Zuckerberg met with a man with the power to influence whether that actually happens.

The Facebook chief executive's meeting with French President Emmanuel Macron on Friday was billed as a chance to find common ground on the regulation of harmful online content.

But looming over the meeting were growing calls in Europe to break up what many have come to see as a social media monopoly.

European Competition Commissioner Margrethe Vestager said in February that while her office was not investigating Facebook, she was monitoring how the company used data.

Her comments came after Germany's antitrust office ruled that Facebook was abusing its dominant market position by combining its data with information from Instagram, WhatsApp and third party websites.

In Macron, Zuckerberg was meeting a power broker who has tremendous sway over how future EU regulators will approach the issue of online data and competition.

Macron's power

With Britain leaving the European Union and German Chancellor Angela Merkel on her way out, Macron has a big role to play in upcoming EU personnel changes.

"Macron thinks he can be the kingmaker ... [with] oversize influence in picking the president of the European Commission," said Celia Belin, a visiting fellow at the Brookings Institution.

He is also likely to have sway over who will replace key EU commissioners, including Vestager. And that makes Macron a very important meeting for Zuckerberg.

Facebook FB declined to comment on whether antitrust issues were discussed on Friday. Zuckerberg said in a statement that the talks focused on issues like privacy, data portability and election interference.

Yet one French official who had lunch with Zuckerberg on Friday, the junior minister for digital affairs Cédric O, told CNN Business that the question of dismantling Facebook is "on the table."

"This question is worthwhile," he said, adding that it's for US and EU regulators to "decide whether there's been a problem with antitrust rules" and whether internet champions should be dismantled.

O said he wants to start with regulation that controls hateful conduct, before considering the kind of antitrust action that Facebook co-founder Chris Hughes proposed earlier this week.

Facebook has pushed back on calls for a breakup.

Nick Clegg, the company's vice president of global affairs and communication, said in a statement this week that "you don't enforce accountability by calling for the breakup of a successful American company."

The centerpiece of France's social media proposals is an internal regulatory system from the companies themselves that would delete hate conduct, with the "duty of care" placed squarely on the platforms.

While Zuckerberg has said he is open to regulation and is engaged in discussions with governments around the world, O said the rules of the road are not for companies to decide.

"It is not for the platforms to decide what justice they should apply. The state makes the rules," he said.