Eric Drouet, a leader of the "Yellow vests" movement, next to his lawyer Kheops Lara (R) as he leaves Paris' courthouse after being detained by the police during a yellow vests demonstration in Paris, Dec. 23, 2018.

Drouet – who already faces a trial for carrying a weapon — was held while heading for the Champs-Elysees, according to a police source.

"Yellow vest" demonstrations — so-called after the high-visibility jackets they wear — began in rural France in November over fuel taxes and ballooned into a wider revolt against President Emmanuel Macron's pro-business policies, which they view as skewed towards the rich.