LITTLE ROCK — A state-approved Ten Commandments monument was erected on the Arkansas state Capitol grounds Tuesday, but its future was uncertain as the American Civil Liberties Union of Arkansas said it would sue to have the marker removed.

The 6-foot-tall granite monument engraved with the Ten Commandments was installed Tuesday morning just southwest of the Capitol, beside the walkway between the Capitol and the Justice Building. The Capitol Arts and Grounds Commission gave final approval to the monument last month, two years after passage of a state law authorizing it.

The American Heritage History Foundation used donated funds to have the monument built and installed. No state money was used, as the 2015 law requires.

State Sen. Jason Rapert, R-Bigelow, who sponsored Act 1231 of 2015, said Tuesday he was “very happy” to see the legislation he sponsored fulfilled.

“We have many monuments scattered around the Arkansas state Capitol grounds that honor many things, and we had none that was dedicated to the moral foundation of the law,” he said.

Rita Sklar, executive director of the ACLU of Arkansas, said the organization is preparing to file a lawsuit. She said the monument violates the First Amendment prohibition against government endorsement of religion and that it is a “specious argument” to claim the monument honors the moral foundation of Arkansas law.

“The Ten Commandments advocate a particular set of religious beliefs,” she said. “For instance: ‘Thou shalt have no other Gods before me.’ That’s a religious obligation. ‘Observe the Sabbath.’ That’s a religious obligation. These are not the basis of Arkansas law. They’re the basis of certain religions.”

Rapert said he believed the monument would survive a constitutional challenge, saying it is identical to a monument on the Texas state Capitol grounds that the U.S. Supreme Court ruled was constitutional in 2005.

Sklar said the Texas monument had been in place for decades and that the nation’s highest high court would view a new Ten Commandments marker differently.

The U.S. Supreme Court ruled in 2005 that a Ten Commandments display at a courthouse in Whitley City, Ky., was unconstitutional. Last year, the Oklahoma Supreme Court ruled that a newly installed Ten Commandments monument outside that state’s capitol building violated the Oklahoma Constitution.

After the Legislature and Gov. Asa Hutchinson approved Act 1231, the state received multiple requests for other monuments at the Capitol, including one honoring the separation of church and state and one in the shape of the Satanic figure Baphomet.

Earlier this year, the Legislature approved a law requiring legislative approval before a monument can be installed on the Capitol grounds. The requested separation of church and state and Baphomet monuments have not been approved by the Legislature or the Capitol Arts and Grounds Commission.

Sklar said the ACLU has talked with the groups that submitted the rejected proposals, but she said the suit would focus not on those refusals but on what the ACLU believes is a violation of all Arkansans’ constitutional rights.

“Everyone in Arkansas should be able to visit the Capitol and not feel like a second-class citizen because of their religious beliefs,” she said.