IN A chilling televised speech last August, Philippine President Rodrigo Duterte read aloud the names of 150 politicians, judges and law enforcement officials, linking them to alleged drug crimes and asking them to surrender themselves to the national police. Since the announcement, many of the people identified have been removed from their positions, denied government security or imprisoned on drug-related charges without due process. Last Sunday, even more disturbing news emerged: One of the politicians named, Ozamiz Mayor Reynaldo Parojinog Sr., was killed in a police raid, along with his wife and 13 others. Mr. Parojinog is the third mayor killed in Mr. Duterte’s “drug war,” which has claimed the lives of more than 7,000 Filipinos.

The Philippine National Police alleges that Mr. Parojinog was killed after his guards opened fire on officers, who were lawfully enforcing a search warrant. This narrative was called into question when details of the raid surfaced the next day. The raid took place at 2:30 a.m. and coincided with the freezing of all closed-circuit cameras in the vicinity. Mr. Parojinog’s daughter, who has been taken into custody on drug and firearm charges, has since accused the police of planting drugs in the home. Given that the two other mayors killed in the drug war were also shot dead by police officers with search warrants, lawmakers and others are right to demand an investigation.

Yet it comes as no surprise that Mr. Duterte has brushed aside all criticism of the police. His government has repeatedly come out in favor of extrajudicial executions in the name of law and order. The country’s police chief has encouraged vigilante killings, while the solicitor general has promised to “neutralize” official inquiries into police practices. Mr. Duterte himself had pledged to execute 100,000 criminals and throw their bodies into Manila Bay. He has also threatened to impose martial law across the country, as he has already done on the island of Mindanao, inspiring little confidence that he will maintain the rule of law.

Congress can take a stand against Mr. Duterte’s assault on basic rights. Sens. Benjamin L. Cardin (D-Md.) and Marco Rubio (R-Fla.) have introduced a bill to restrict the supply of defense equipment to the Philippine National Police, the force that is leading the drug war. This act could be a strong rebuke to Mr. Duterte, especially if it is supplemented with calls for an independent U.N. investigation into the government’s brutal anti-drug campaign.

Secretary of State Rex Tillerson should deliver this message personally during his upcoming visit to Manila. Doing so might irritate Mr. Duterte, but that would do less lasting harm to U.S.-Philippine relations than would setting aside democratic values for geopolitical convenience. Most Filipinos look on the United States favorably; how long will that last if America finds nothing objectionable in Mr. Duterte’s frighteningly lawless regime?