A prominent Muslim advocacy organization is taking Texas to court, arguing that Gov. Greg Abbott’s decision to brand it a “foreign terrorist organization” tramples both the U.S. Constitution and state law.

The Council on American-Islamic Relations’ (CAIR) Dallas-Fort Worth and Austin chapters filed a federal lawsuit Thursday seeking to overturn Abbott’s proclamation issued earlier in the week.

“This attempt to punish the nation’s largest Muslim civil rights and advocacy organization simply because Governor Abbott disagrees with its views is not only contrary to the United States Constitution, but finds no support in any Texas law,” the group said in its lawsuit.

Founded in 1994, CAIR operates 25 chapters nationwide, including a small Texas staff of eight employees and two contractors, according to the filing.

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“CAIR-Texas and the Texas Muslim community are standing up for our constitutional rights by directly confronting Greg Abbott’s lawless attack on our civil rights,” CAIR-Texas said in a statement. “We are not and will not be intimidated by smear campaigns launched by Israel First politicians like Mr. Abbott. Mr. Abbott is defaming us and other American Muslims because we are effective advocates for justice here and abroad. We plan to continue exercising our constitutional rights, defending civil rights, and speaking truth to power, whether in defense of free speech, religious freedom and racial equality here in Texas or in defense of human rights abroad.”

Abbott’s order extended the “terrorist” label to the Muslim Brotherhood, even though federal authorities have never classified either group that way.

The governor’s decree also bars CAIR from purchasing land in the Lone Star State under a new statute aimed at curbing purchases tied to “foreign adversaries.”

The group’s filing contends Abbott relied on “inflammatory statements with no basis in fact,” selectively citing remarks by affiliates to paint CAIR as sympathetic to terrorism.

“The lawsuit we have filed today is our first step towards defeating Governor Abbott again so that our nation protects free speech and due process for all Americans,” CAIR Litigation Director and General Counsel Lena Masri said in a statement. “No civil rights organizations are safe if a governor can baselessly and unilaterally declare any of them terrorist groups, ban them from buying land, and threaten them with closure. We have beaten Greg Abbott’s attacks on the First Amendment before, and God willing, we will do it again now.”

The Muslim Legal Fund of America also said it is “proud to defend the constitutional rights of CAIR-Texas and the right of all Texans to engage in free speech and uphold civil rights without facing lawless and defamatory attacks by Greg Abbott.”

“Mr. Abbott’s unconstitutional proclamation undermines the very foundational notions of due process that our system depends upon and it must not stand,” said Muslim Legal Fund of America attorney Charlie Swift. “For the sake of our nation’s basic freedoms, Greg Abbott’s latest attack on the American people must be defeated.”

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Earlier this year, Texas Republicans sought to stop a Muslim-centered planned community around one of the state’s largest mosques near Dallas.

Abbott and other Republican state officials opened investigations into the development linked to the East Plano Islamic Center (EPIC), claiming the group is attempting to create a Muslim-exclusive community that would implement Islamic law.

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EPIC City representatives called the attacks alleging Islamic law misleading, dangerous and without basis.

The U.S. Justice Department closed a federal civil rights investigation into the planned community without bringing any charges or lawsuits.

The Associated Press contributed to this report.