That move came as activists seeking to criminalize ecocide had been laying the groundwork for a landmark change to the court’s remit . Their plan is to get a state that is party to the Rome Statute — or a coalition of them — to propose an amendment to its charter establishing ecocide as a crime against peace. At least two-thirds of the countries that are signatories to the Rome Statute would have to back the initiative to outlaw ecocide for the court to get an expanded mandate, and even then it would only apply to countries that accept the amendment. Still, it could change the way the world thinks about environmental destruction.

Richard Rogers, a lawyer who specializes in international criminal law and human rights, said that if ecocide campaigners and countries suffering the effects of climate change put forward a narrow definition of the crime, it could quickly garner widespread support. “We’ve seen in the past few years a huge shift in public opinion, and we’re entering a phase where there is going to be huge pressure on governments to do more,” said Mr. Rogers, a partner at Global Diligence, a firm that advises companies and governments on risk mitigation.

Given the number of countries and businesses that would recoil at the prospect of being held criminally responsible for environmental damage, he said, it is vital to come up with criteria that reserve prosecution for cases in which “massive and systematic” environmental destruction is done “knowingly or intentionally.”

Environmental activists say there is no shortage of culprits who could be put on trial if the world were to decide to outlaw ecocide. But few are as compelling as Mr. Bolsonaro, a far-right former Army captain who campaigned on a promise to roll back the land rights of indigenous people and open protected areas of the Amazon to mining, farming and logging.

From an evidentiary standpoint, Mr. Bolsonaro is an attractive potential defendant because he has been so starkly disdainful of his own country’s environmental laws and regulations. He vowed to put an end to fines issued by the agency that enforces environmental laws. He has asserted that protecting the environment matters only to vegans. He complains that Brazil’s 1988 Constitution set aside too much land to indigenous communities who “don’t speak our language.”

Since Mr. Bolsonaro took office in January, deforestation in the Amazon has increased significantly, setting the stage for the thousands of fires that began raging last month. Government agencies tasked with protecting the environment warn meanwhile that they are at a breaking point as a result of budget and personnel cuts.

Mr. Bolsonaro is by no means the only world leader reviled by environmentalists. President Trump has been assailed for rolling back environmental regulations and pulling out of the Paris climate accord.