In France, where fashion is considered part of the patrimony and first ladies have been front-row regulars (and supermodels), the government has long treated the industry with kid gloves. Then, in 2017, Brune Poirson arrived.

“In the beginning, everybody thought I was crazy,” said Ms. Poirson, who is officially one of three secretaries of state to the minister for the ecological and inclusive transition and, unofficially, France’s de facto minister for fashion.

Both a champion of the industry and its rare critic, Ms. Poirson, 37, is playing a role in negotiations regarding President Trump’s threats to impose tariffs on handbags and other luxury goods, also known as the “handbag war.” Last year, she also spearheaded wide-ranging legislation that included banning brands from destroying an estimated 630 million euros (or $700 million) of unsold goods annually, a common practice in the industry. Prime Minister Édouard Philippe has said France would be the first to formally adopt this measure.

“When you’re a young woman in government — or in general, in life — and you decide to tackle a topic like fashion, everybody goes after you,” she said in an interview. “It’s almost the end of your reputation. If I were really a politician, I would have taken nuclear energy or something. But I think there is more to do in the field of fashion. I know we need to do something about it.”