"A fine of 2,000 thousand euros, of which 500 euros is suspended", Drouet's lawyer Kheops Lara told reporters.
Lara said he regretted the court's decision, adding that he intends to protest the sentence.
"This is fine, which may seem almost insignificant… But it still remains a criminal sentence. I think that this decision will damage the image of France and the French justice", the lawyer said.
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Drouet himself was not present at the court session, as he was busy with his job, the lawyer explained.
"He works, even at night… But I immediately informed him of the court decision. I think he will speak out pretty quickly", Lara added.
Lara also recalled that two weeks ago Drouet had publicly said that he had stopped participating in protest rallies and intended to look for other ways of action for the "yellow vests".
"I do not know whether he would participate in the rally tomorrow", the lawyer added.
Drouet, who was one of the initiators of the first yellow vests rally, was twice detained by law enforcement agencies during demonstrations on 22 December and 2 January for organising unauthorised rallies. On 5 June, Drouet will be tried again over "carrying of prohibited weapons" at the rally on 22 December.
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The wave of the yellow vests rallies started in France in mid-November over planned hikes in fuel taxes. While the French government abandoned its plans to raise fuel taxes and introduced other measures to improve the country's socioeconomic situation, protesters continue to take to the streets across France every weekend for demonstrators to express their discontent with government's policies.