ADDIS ABABA, Ethiopia — On a bright day in mid-November, about a dozen police officers with machine guns barged into the home of Lisanewerk Desta, a theologian who is the head of the library and museum department at the Ethiopian Orthodox Church, and got to work.

The men, who had no warrant, Mr. Desta said, poured dried goods from his kitchen onto the floor, emptied his clothes drawers and even looked inside his clay coffee pot, seemingly searching for something to incriminate him. They confiscated only one item, he said: his Ethiopian identification card, which shows that he is from the Tigray ethnic group.