A new French law that would have required such social media platforms as Facebook to take down objectionable content within 24 hours has been rejected by France's Constitutional Council as a disproportionate response to the proliferation of hate speech online.

The ruling is a limited victory for free-speech advocates and a temporary reprieve for Facebook and other platforms, which under the new law would have faced heavy costs for real-time mediation of content and heavy fines for failure to comply, media lawyers told Law.com International.

France's Conseil Constitutionnel, the equivalent of the Supreme Court, ruled on June 18 that the new Loi Avia, which had passed both houses of the French parliament, would infringe "freedom of expression and communication" in a way that was "not appropriate, necessary and proportionate to the goal being pursued."

The ruling leaves intact the body of French law that prohibits hate speech, a category that includes racial slurs, denial of the Holocaust, and incitement to violence.

But it sends the government back to the drawing board to find a more nuanced way to make platforms such as Facebook and Twitter, and their powerful corporate owners, responsible for the content posted by users.

"The intentions behind the law were good," said Basile Ader, a media law partner at August Debouzy in Paris. "But the Constitutional Council made it clear that these goals should be achieved in a measured, proportionate way—not with a hatchet."

The law and its potential application to Facebook made headlines in France earlier this month after a French website published screen grabs of racist comments that appeared in a private Facebook group for 8,000 law enforcement agents. The publication came amid protests in France and around the world of the killing of men and women of color by police officers.

The French interior minister, Christophe Castaner, said the government would sue to compel Facebook to divulge the names of the people posting the content so that they could be prosecuted for public hate speech. Under French law, private social media groups are considered public once they reach a certain size, and law enforcement officers are held to a higher standard of public expression.

Under the Loi Avia, Facebook would have been compelled to take the comments down, Ader of August Debouzy said.

"But with the core of that law now rejected, the situation is more complicated," he said. "The government will need to find another way to make the platforms take more responsibility."

The approval and disapproval of the Loi Avia highlight not only the intellectual challenge of policing free speech in a democracy, but also the technical challenge of policing social media platforms where communications are instantaneous and round the clock, lawyers said.

In its ruling, the Constitutional Council noted the provisions of the new law that would have required platforms to take down objectionable content within 24 hours or face heavy fines.

Julien Guinot-Deléry, a media law counsel at Gide Loyrette Nouel, explained that in order to react that quickly, the platforms would either have to set up 24/7 content review by human moderators or get any post-publication complaints before a judge within 24 hours, the latter an impractical and unlikely outcome, he said.

What was more likely, he said, is that the platforms would set up an automated system to immediately take down any content that drew a complaint.

It is this outcome, Guinot-Deléry said, that raised the possibility before the constitutional body that the law, as written, posed too great a risk of overregulation.

"When you're talking about a cornerstone issue like freedom of expression, it's difficult to see how you can neglect the human element," he said.