President Rodrigo Duterte of the Philippines relishes his image as a defiant crusader, willing to encourage the slaughter of thousands in the name of saving his nation from the scourge of drugs. More than 7,000 suspected drug users and dealers, witnesses and bystanders — including children — have been killed by the police or vigilantes in the Philippines since last July.

The man is impervious to moral criticism, but he may not be immune forever from legal action. Last Thursday, the Philippine lawmaker Gary Alejano filed an impeachment complaint against Mr. Duterte, accusing him of corruption, murder and crimes against humanity in connection with his bloody antidrug campaign. “We are of the firm belief that he is unfit to hold the highest office of the land,” Mr. Alejano said.

With Mr. Duterte’s allies holding an overwhelming majority in the House of Representatives, there is little chance he will be impeached. But exhausting domestic remedies, such as impeachment, could clear the way for jurisdiction by the International Criminal Court. Jude Josue Sabio, a lawyer for two men who say they belonged to a death squad that operated under Mr. Duterte when he was the mayor of the city of Davao, says he intends to bring a case against Mr. Duterte in The Hague. Ever defiant, Mr. Duterte said on Sunday that he welcomed a trial by the court, and vowed his drug war “will continue and it will be brutal.”