Tens of thousands of people may have died amid a crackdown on the drug trade launched by Duterte after he was elected president in 2016. Human rights groups have accused police of killing people with no connection to illicit drugs. In March 2019, the Philippines withdrew from the International Criminal Court after it opened a preliminary inquiry into the country's drug war.
The bishops' letter also lamented the closure of ABS-CBN, the country's largest broadcasting network, following a dispute with the government.
"Is it not evident to us how this pattern of intimidation creates an atmosphere detrimental to the freedom of expression in our country?" the bishops wrote, welcoming challenges to the constitutionality of the Anti-Terror Act at the country's Supreme Court.
They compared the present situation in the Philippines to that of 1972, when President Ferdinand Marcos imposed martial law, ushering in a period of dictatorship.
"The return of 'warrantless detentions' through this new law cannot but remind us of the initial moves in 1972 that eventually led to the fall of democracy and the rise of a dictatorial regime that terrorized the country for 14 years," the bishops wrote.
"It all began when an elected president also legalized the 'ASSOs' (arrest, search and seizure orders). It was from there that we gradually sank into the mire of authoritarian rule. Knowing how, in just the recent past, the law has been used too many times as a weapon to suppress legitimate dissent and opposition, we cannot but share in the apprehensions expressed by the lawyers and ordinary citizens that filed the petition against the said infamous law before the Supreme Court."
The bishops praised public officials who continued to resist political pressures, but said they wished there were more of them.
Duterte, an outspoken critic of the Church, is expected to end his term as president June 30, 2022. He is scheduled to give his fifth State of the Nation Address July 27.
The bishops ended the pastoral letter with a prayer asking God to overcome the country's divisions and give public servants "the courage to stand their ground on the side of truth and justice."