All but one of the members of an Iraqi delegation of minority groups—comprising representatives of the Yazidi and Turkmen Shia religious communities—have been granted visas to come for official meetings in Washington. The lone member denied a visa was the only Iraqi Christian in the group, a Catholic nun.

Nina Shea, director of Hudson Institute’s Center for Religious Freedom, reported Thursday that the U.S. State Department prevented a persecuted Iraqi Catholic nun named Sister Diana Momeka, “an internationally respected and leading representative of the Nineveh Christians who have been killed and deported by ISIS,” from coming to Washington to testify.

Sister Diana is a member of the Dominican Sisters of Saint Catherine of Siena, a Catholic order of nuns that traces its presence in Iraq back to the thirteenth century.

The nun is uniquely qualified to testify to Islamic State atrocities in Iraq. When Mosul was overrun by Islamic extremists in June 2014, about 500,000 civilians left the city en masse, in an effort to escape the siege. At that time, the only group that chose to remain in Mosul was the Dominican Sisters of St. Catherine of Siena, “a congregation of Iraqi sisters that has witnessed generation upon generation of war and carnage.”

On Tuesday, however, the U.S. consulate in Erbil told Sister Diana that her visa application had been denied, stating that she was unable “to demonstrate that [her] intended activities in the United States would be consistent with the classification of the visa.”

The nun told Nina Shea she was informed she was rejected because she is an “IDP,” an Internally Displaced Person. In other words, the State Department suspected that the Catholic nun could be secretly intending to stay in the United States.

Never mind that Sister Diana already had meetings set up with the Senate and House Foreign Relations Committees, the State Department, USAID, and several NGOs, or that she submitted several documents attesting to her character, as well as the temporary nature of her stay in the U.S.

She is, in fact, contracted to teach at the Babel College of Philosophy and Theology in Erbil, Kurdistan, for the 2015–16 academic year.

Moreover, Sister Diana had already been permitted to visit the United States, and she delivered the commencement address at Chicago’s Catholic Theological Union in 2012.

According to Shea, the nun has become internationally known as a spokesperson for the over 100,000 Christians driven into Kurdistan under the ISIS “convert or die” policy. Former Congressman Frank Wolf (R. – Va.) met her in Kurdistan a few months ago and agreed to sponsor her trip to the U.S. to tell her story.

Wolf, cofounder of religious freedom group 21st Century Wilberforce Initiative, said they had hoped to facilitate her trip to the states “so that she could speak with great candor, as is her custom, to policymakers.” Wolf said that he views her as “a critical voice to awaken the church in the West to the suffering of Christians and other religious minorities in Iraq.”

For some reason, the U.S. consulate does not see it this way. According to Shea, the State Department has pledged that “every overseas post and domestic bureau will seek opportunities to engage religious leaders” as part of its program for countering “violent extremism.”

Apparently, Catholic nuns do not fit the bill.

Follow Thomas D. Williams on Twitter @tdwilliamsrome.