On a recent Sunday morning, Donald Ossewaarde, a Baptist preacher from the United States, hosted an informal Bible study group at his home in Oryol, a small city 225 miles south of Moscow. Most of the dozen or so people who attended had been coming to Ossewaarde’s weekly gatherings for years, and they were looking forward to an hour of Christian song, prayer and discussion.

But as the lesson began, three police officers walked into Ossewaarde’s house. They waited silently until the lesson was over, then started questioning everyone, and they eventually insisted that Ossewaarde and his wife, Ruth, accompany them to the local police station. There, the police told Ossewaarde that a woman had filed a complaint against him, saying she was outraged that “foreign religious cultists” were allowed to operate in the city.

At a hastily arranged court hearing just hours after his arrest, a judge found Ossewaarde guilty of illegal missionary work and fined him 40,000 rubles (about $600). For Ossewaarde, a fluent Russian speaker who has lived in Oryol since 2002, the court’s ruling was shocking. “We had been perfectly free all these years to give out literature, to talk to people on the street,” he says. “People have either been friendly or indifferent.”

Not anymore. In July, Russian President Vladimir Putin signed a new law that cracks down on missionary work and evangelism. Among other things, it mandates that people share their religious beliefs only at state-registered places of worship. Critics say the law, which was approved as part of a swath of “anti-extremism and terrorism” legislation, contradicts Russia’s post-Soviet constitution, which guarantees citizens and foreigners the right to disseminate their religious beliefs. “Soviet history shows us how many people of different faiths have been persecuted for spreading the word of God,” wrote Sergei Ryakhovsky, head of the Protestant Churches of Russia, in an open letter to Putin. “This law brings us back to that shameful past.”

The law comes at a time when the Kremlin is pushing a major anti-Western propaganda campaign, from accusing the U.S. and U.K. of plotting to overthrow Putin to boasting about Moscow’s ability to reduce the U.S. to “radioactive ash.” And so far, the consequences of the law have exclusively affected members of minority “foreign” religions—the Church of Jesus Christ of Latter-Day Saints, the International Society for Krishna Consciousness, Jehovah’s Witnesses and Protestants with Baptist, Pentecostal and Seventh-day Adventist roots. Believers of these religions have frequent problems gaining state permission for churches and temples, and they often have little choice but to gather informally at the homes of their congregants.

The Russian Orthodox Church, a powerful Kremlin ally that has traditionally been hostile to minority faiths, has not been affected, and Orthodox officials have dismissed criticism of the law, saying it does not prevent believers from sharing their faith. Russia’s Muslims, who make up some 10 percent of the population, seem divided on the legislation, with regional muftis split on whether it’s a gross violation of human rights or a necessary step in the fight against Islamic extremism.

Ossewaarde believes it’s the former. Two days after his conviction, he received a warning from his court-imposed lawyer, Andrey Butenko; if he and his wife chose to stay in Russia, the lawyer said, they could be in danger. Concerned that Butenko’s warning was an indirect message from the authorities, Ruth Ossewaarde flew to the United States on August 22. Donald Ossewaarde remained in Oryol to appeal his conviction.

Butenko tells Newsweek he was not acting on anyone’s orders and says his warning was inspired by genuine concern for the couple’s well-being. “All religions except traditional Russian faiths are being slowly forced out of Russia,” he says. “The state will do whatever it thinks it needs to do in order to achieve this. This is how the security forces work. If they need to, they could do something bad to him.”

The Ossewaardes are not the only ones who have been affected by the crackdown. In late July, police officers detained Ebenezer Tuah, a student from Ghana, as he carried out a baptism at a swimming pool in Tver, a small city near Moscow. Tuah and a group of Ghanese nationals had rented the pool for their Protestant group for the day, and there were no Russian citizens present. The officers handcuffed Tuah and kept him overnight in a police station. The authorities later fined him 50,000 rubles (about $780) for “conducting religious rites and ceremonies” without the necessary documents. (He declined to comment on the matter.)

“They treated him like a common criminal,” says Konstantin Andreev, a lawyer at the Slavic Center for Law and Justice, which has filed appeals against the convictions of both Ossewaarde and Tuah, as well as others charged under the new law.

Andreev, who is also a Protestant preacher, believes the legislation is part of a broader crackdown on civil liberties that has occurred since Putin became president for the third time, amid mass protests, in 2012. He says the courts and police officers enforcing the law are doing so with a flawed understanding of it, as the law technically concerns only members of organized religious groups who are attempting to convert those who do not share their faith. In reality, critics say, the authorities can label almost any religious activities not carried out in state-registered churches as missionary work or evangelism.

“This law has been joyfully welcomed by nationalist-minded people, who say at last we have a means of fighting against those who are not Russian Orthodox Christians and do not share our ideas,” Andreev says.

Mormons in particular have experienced problems since the law came into effect. In August, Russian authorities deported six Mormon missionaries for allegedly violating compulsory registration requirements. Although the deportations were not directly linked to the law on sharing beliefs, analysts say the expulsions are part of a new intolerance for foreign religions in Russia. “Lawmakers have decided that missionaries are dangerous people,” says Roman Lunkin, a religion analyst at the Russian Academy of Sciences in Moscow. “They have been stripped of the right to the presumption of innocence.”

Some members of the Russian Orthodox Church have also criticized the legislation. “This law plainly contradicts the Gospels,” wrote Karina Chernyak, who runs an Orthodox Christian youth club in Moscow, in an article for the Sova Center, a nonprofit that monitors religion and Russian society. “It is the mission of every Christian to go and teach his or her belief to others. In many ways, this is the essence of belief.”

Back in Oryol, Ossewaarde is preparing for his appeal, which is set for September 19. And for now, he has shuttered his Bible study group. A Russian-language notice on the door of his home reads: “Dear friends! Until further notice, there will be no meetings here. There is an official assertion that these activities are illegal. Sorry for the inconvenience. Donald.”