The Russian Supreme Court could declare the Jehovah’s Witnesses an extremist organization in a Wednesday hearing, a move that would lead to the seizure of the church’s headquarters near St. Petersburg and the outlawing of the group’s organized worship.

In advance of the hearing, international concern has grown. “If the Supreme Court rules in favour of the authorities, it will be the first such ruling by a court declaring a registered centralized religious organization to be ‘extremist,’” the UN human rights’ high commissioner’s office said in a statement on Tuesday.

The ruling would also cap off years of increased restrictions by the Russian Federation against minority religions. Last summer, Russia introduced an anti-terrorism law that also restricted evangelism, and a regional court ordered the deportation of six missionaries with the Church of Jesus Christ of Latter-day Saints. In 2015, a court banned the Church of Scientology’s Moscow branch.

Under a Russian law passed in 1997, there is freedom of religion, but four faiths are designated to be traditional—Orthodox Christianity, Islam, Judaism, and Buddhism—and other religious organizations must register with the government. Some groups, like Jehovah’s Witnesses, who are registered, still face bureaucratic and legal hurdles. Jehovah’s Witness leaders estimate that there are 175,000 Russian-based adherents to the faith, which was founded in the United States the 1870s. Unlike Catholic, Protestant, and Orthodox Christians, Jehovah’s Witnesses believe that Jesus is the son of God but do not believe in the Trinity.

“They would basically be prosecuting Jehovah’s Witnesses as criminals,” David Semonian, international spokesperson for the Jehovah’s Witnesses, says of the pending court declaration. “Anyone who would actually would have our publications could be criminalized. It is of great concern.”

Jehovah’s Witnesses have filed a counter claim asking the court to rule the Justice Ministry’s actions as political repression. A ruling in favor of the ministry would make it a crime for Jehovah’s Witnesses to worship in the Russian Federation and dissolve the faith’s legal means to own or rent Kingdom Halls, their places of worship. In 2015, the Russian Federation banned the Jehovah’s Witnesses’ website JW.org, and customs officials stopped shipments of Jehovah’s Witnesses’ Bibles, citing the possibility they were extremist literature. Last year, Russia threatened to close the group’s national headquarters.

Roman Lunkin, a human rights fellow at the Wilson Center and an expert on church-state relations in Russia, says that Russian authorities have been targeting minority religions as “extremists” in an effort to demonstrate support for the Russian Orthodox Church and to marginalize organizations with suspected pro-western sympathies. “The treatment of the Jehovah’s Witnesses reflects the Russian government’s tendency to view all independent religious activity as a threat to its control and the country’s political stability,” the U.S. Commission on International Religious Freedom said in a statement on Tuesday.

“Jehovah’s Witnesses are no threat to either the Russian Orthodox Church or to the Russian Government,” Semonian says. “The constitution guarantees freedom of worship, and that is all we are asking, to have the same rights as other religious groups have so we can go about our ministry in a peaceful way.”

Jehovah’s Witnesses are pacifists, and their religious beliefs require them to abstain from political activity. They declare allegiance only to God, not to a state or political entity. They do not vote, lobby, protest, or join military. This lack of participation can be seen as a threat if a state demands nationalist and patriotic activity.

“The persecution of the Jehovah’s Witnesses is very much tied to the resurgence of a new view of nationalism, where everything within the state is fine, but anything outside of the state has to be crushed,” Kristina Arriaga de Bucholz, a U.S. commissioner for International Religious Freedom appointed by House Speaker Paul Ryan, says. “A pacifist group that tells its members that their allegiance is to something outside of the government is immediately a group that will be perceived as dangerous to the regime.”

Other minority Christian groups in Russia, like evangelicals, have not yet faced the same level of scrutiny. Lunkin says it is impossible to accuse evangelicals of extremist activity because their literature and Bible translation matches that of the Russian Orthodox Church. Jehovah’s Witnesses have their own translation of the Bible, and they also have their own magazine and educational materials. Evangelicals also have closer relationships with government officials, he says. “It’s [about] a protection of traditional religions, and the Orthodox identity of Russian people,” Lunkin says. “But in fact it is about protecting personal power, because the main fear is changing of regimes in Russia.”

Jehovah’s Witness church leadership has reached out to the U.S. State department’s Office of International Religious Freedom, the U.S. Commission on International Religious Freedom, and the U.S. Helsinki Commission for aid. “We will do everything within our legal means to have the judgment reversed,” Semonian says. “Jehovah’s Witnesses are known worldwide for our peaceful activities, and under no circumstances would we ever resort to violence or any other activity that could be misunderstood or considered extremist.”

Jehovah’s Witness leaders have also asked their eight million members worldwide to write letters to Russia officials, including President Vladimir Putin and Prime Minister Dmitry Medvedev, to ask them to intervene. Instructions tell writers to “be candid but respectful,” and to mention how the faith has benefited their families. “Keep in mind that ‘a mild answer turns away rage,’ and ‘a gentle tongue can break a bone,’” the instructions say, quoting the Biblical book of Proverbs.

The decision will come as the U.S. Commission on International Religious Freedom is finalizing its annual report identifying countries of concern, its first such report for the Trump administration. The Commission is a bipartisan government advisory group that makes policy recommendations to the President, Congress, and the Secretary of State.

Since 2009, the group has designated Russia as a “Tier 2” nation, on the watch list one step below countries of particular concern. “The fate of the Jehovah’s Witnesses is the fate of any religious group that does not pledge its allegiance to the Russian government,” Arriaga says. “April 5 will definitely mark a new chapter of religious persecution in post-Soviet Russia.”