Summum, a small Salt Lake City religious group that wants to place a granite marker in a Pleasant Grove park, may have lost its first battle before the highest court in the land.

But Summum attorney Brian Barnard said the U.S. Supreme Court's ruling Wednesday opens the door to a new constitutional challenge as the case returns to U.S. District Court in Salt Lake City.

"It's like they are handing it to me on a silver platter," said Barnard, who intends to amend the lawsuit, adding church-state separation claims.

Likewise, the American Humanist Association cheered the court's decision, saying it provides a path to getting all Ten Commandments monuments off public property in the United States.

The Supreme Court ruled unanimously Wednesday that Pleasant Grove did not violate Summum's free-speech rights when the city refused permission for Summum to place a marker listing its Seven Aphorisms in Pioneer Park.

The Ten Commandments monument that is already in Pioneer Park is clearly government speech, not private speech protected by the First Amendment's Free Speech Clause, said the court in an opinion written by Justice Samuel Alito.

Cities and other government entities have a right to select monuments that reflect the local aesthetics, history or culture, the opinion said.

"City parks, ranging from those in small towns, like Pioneer Park in Pleasant Grove City, to those in major metropolises, like Central Park in New York City, commonly play an important role in defining the identity that a city projects to its own residents and to the outside world," the opinion said.

A public park can provide a "soapbox" for a range of orators, "but it is hard to imagine how a public park could be opened up for the installation of permanent monuments by every person or group wishing to engage in that form of expression," the opinion said.

Pleasant Grove Mayor Mike Daniels said the decision affirms what the city believed all along: The park reflects the city's identity and culture.

"[The decision] means the city can continue to collect and display artifacts relevant to its history in its outdoor park," Daniels said Wednesday.

The attorney who argued the case for the city called it a "landmark" decision that will act as a bookend on years of litigation about display of the Ten Commandments around the country.

"This decision represents a resounding victory for government speech," said Jay Sekulow, chief counsel for the American Center for Law and Justice. "The decision gives government the right to speak for itself and the ability to communicate on behalf of its citizens."

Now that the Supreme Court has determined that the Ten Commandments monument in Pleasant Grove constitutes that city's speech, Barnard will amend the Summum lawsuit to claim the city is blurring the church-state line, a claim that has not been raised in this case. The U.S. Constitution's Establishment Clause forbids government from favoring one religion over another.

The American Humanist Association announced in a news release that it will help Summum pursue the claim -- or file its own.

"We humanists are ready to argue that Ten Commandments monuments in U.S. public parks are unconstitutional government endorsements of religion," said Bob Ritter, legal coordinator for the Appignani Humanist Legal Center of the American Humanist Association, in a news release.

A Washington attorney for Pleasant Grove, however, said that surely Barnard and the Humanists know any such claims would be "flat-out losers."

In 2005, The Supreme Court decided in Van Orden v. Perry that Ten Commandment monuments on public property do not violate the separation of church and state, according to Francis J. Manion of the American Center for Law & Justice.

The Becket Fund for Religious Liberty praised the court's conclusion that governments can accept some monuments in public parks and reject others.

"The court has carefully drawn a line between private speech and government speech that protects both local governments from a wave of clutter and religious speakers from government discrimination," said Eric Rassbach, national litigation director of the Becket Fund, in a statement.

Before the Pleasant Grove case, a number of Utah governments, facing lawsuits and preliminary court losses, chose to move Ten Commandments monuments rather than allow Summum to place markers of its Seven Aphorisms. Ogden, Salt Lake County, Murray and Tooele City all removed Ten Commandments monuments. Most ended up on private property.

Ogden Mayor Matthew Godfrey said Wednesday that his municipality feels vindicated for its earlier -- if less successful -- battle against Summum. Godfrey said Ogden will consider placing a Ten Commandments monument back on the municipal building grounds.

Tribune reporters Donald W. Meyers and Christopher Smart contributed to this story.