The so-called "Duplomb law" has sparked public anger for permitting a return of acetamiprid -- a chemical known to be toxic to pollinators, such as bees, and to the environment.

A student-led petition against the bill garnered more than two million signatures after lawmakers adopted its reintroduction on July 8, when it was rushed through a deeply-divided lower house of parliament without a proper debate.

President Emmanuel Macron has said he is waiting to hear the verdict of the Constitutional Council, which is expected to deliver its ruling on the constitutionality of the law at 6:00 pm (1600 GMT).

If the law is upheld, Macron will have two weeks to enact it or request a second vote in parliament.

Banned in France since 2018, acetamiprid remains legal in the European Union, and proponents say that some French farmers need it to help them compete economically.

The insecticide is particularly sought after by beet and hazelnut growers, who say that they have no alternative against pests and face unfair competition.

But the petition on France's lower-house National Assembly's website, which has garnered more than 2.1 million signatures, calls the measure a "frontal attack on public health".

Beekeepers have described the chemical as "a bee killer", and its effects on humans are also a source of concern, though its risk remains unclear in the absence of large-scale studies.

Left-wing lawmakers, who referred the bill for constitutional review, said it violates France's environmental charter which guarantees the "right to live in a balanced and healthy environment".

For some opponents, frustration stretches beyond environmental and health concerns to exasperation over the country's political deadlock.

One supporter of the petition called it "democratic revenge" after Macron forced a controversial pension reform through parliament in 2023 and dissolved the lower chamber last year, sparking political turmoil that resulted in a hung parliament.

According to a poll published in La Tribune Dimanche in late July, 64 percent of people surveyed hope that Macron will not sign the bill into law but will instead submit it to a new debate in parliament.

In late June, before the law's passage, several thousand demonstrators - including farmers, environmental organisations and scientists -- rallied across France calling for the bill to be withdrawn.