PARIS — After 30 years of fraught attempts to make France’s labor market more flexible, the government announced sweeping changes on Thursday with the potential to radically shift the balance of power from workers to employers.

The step was the first of several that President Emmanuel Macron and his government are planning to take to galvanize the French economy. It was cheered in European capitals, where an invigorated France is considered critical to the survival of a European Union that is finally showing signs of revival after a lost decade.

The changes to France’s labor rules, the Code du Travail, have proved contentious for Mr. Macron. The young president toppled the old political order with his election just three months ago and his popularity has already slumped in part because of the uncertainly surrounding his labor reform effort.

Economists in France and across Europe expressed optimism about the new law, however, suggesting that Mr. Macron had seized the moment just after his election, when the country might be more receptive to what was being characterized as a revolutionary change.