The US Supreme Court has ruled that a Utah city did not violate the free speech rights of a religious sect when it refused to place the group's monument beside an existing Ten Commandments monument in a public park.

Lawyers for the Summum religion insisted in a lawsuit that the placement of the Ten Commandments monument in a Pleasant Grove City park created a public forum that required the city to accept other kinds of monuments and messages.

When Pleasant Grove refused to accept Summum's monument, the group sued the city for engaging in unconstitutional censorship. A federal appeals court agreed. The city was ordered to erect the Summum monument.

In a unanimous decision announced Wednesday, the Supreme Court reversed that decision. The high court said that when a government entity decides to place a privately donated monument on public land, the display represents the government's own speech and does not require government acceptance of any and all other monuments conveying competing messages private groups may want displayed.

"Government decisionmakers select the monuments that portray what they view as appropriate for the place in question, taking into account such content-based factors as esthetics, history, and local culture," Justice Samuel Alito wrote for the court in an 18-page decision. "The monuments that are accepted, therefore, are meant to convey … a government message, and they thus constitute government speech."

The decision in Pleasant Grove City v. Summum is important because it marks the latest expression of an emerging doctrine in Supreme Court jurisprudence setting the limits and powers of government speech.

"The decision gives government the right to speak for itself and the ability to communicate on behalf of its citizens," said Jay Sekulow, chief counsel at the American Center for Law and Justice, who argued the case for Pleasant Grove.

"It's a landmark decision that clears the way for government to express its views and its history through the selection of monuments – including religious monuments and displays," Mr. Sekulow said in a statement.

The decision is raising concern among some analysts that it might encourage government officials to approve religious displays on public land.

"Government has no business erecting, maintaining, or promoting religious symbols or codes," said the Rev. Barry Lynn, executive director of Americans United for the Separation of Church and State. "The answer in this case is to remove the Ten Commandments from the public park, not compound the problem by adding more sectarian material," he said in statement.

Although the Pleasant Grove case was litigated under the First Amendment's free speech clause, both sides waged the battle with an eye toward the First Amendment's establishment clause.

At first, Pleasant Grove was reluctant to claim responsibility for the religious message associated with the Ten Commandments monument in its park. City officials were concerned that if they made their case too vigorously, the courts would find that the monument amounted to an unconstitutional establishment of religion and order it removed.

Lawyers for the Summum religious group said the Ten Commandments and other monuments in the park created a public forum and that the First Amendment prohibited the government from picking and choosing which messages to display.

Summum is a religious group founded in 1975 in Salt Lake City. Its followers believe that in addition to the Ten Commandments, Moses also brought 'Seven Aphorisms' down from Mt. Sinai. In 2003, the group asked to erect a 'Seven Aphorisms' monument beside the city's Ten Commandments monument. They said they had a free speech right to do so.

A panel of the Denver-based 10th US Circuit Court of Appeals agreed with Summum. Pleasant Grove appealed that decision in the Supreme Court.

Summum warned that the government speech argument could be used as a subterfuge to allow public officials to use public land and resources to advance messages of favored religions over messages of other faiths. Such favoritism is unconstitutional.

Justice Alito said Summum had raised a legitimate concern. But he said privately donated monuments on public land frequently convey more than one message. "By accepting such a monument, a government entity does not necessarily endorse the specific meaning that any particular donor sees in the monument," he wrote.

Alito said erecting monuments in a public park is not the equivalent of delivering speeches or holding demonstrations in a public park. "Speakers, no matter how long-winded, eventually come to the end of their remarks; persons distributing leaflets and carrying signs at some point tire and go home; monuments, however, endure."

He added: "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."

Lawyers for Pleasant Grove and friend of the court briefs filed on the city's behalf warned that if Summum's position was upheld, all public parks would potentially become cluttered with monuments containing competing messages.

When France gave the United States the Statue of Liberty, would the government have been obliged to accept a 'Statue of Autocracy' from the German Empire or imperial Russia, Alito asked.

"If government entities must maintain viewpoint neutrality in their selection of donated monuments, they must either brace themselves for an influx of clutter or face the pressure to remove longstanding and cherished monuments," Alito wrote.

"The obvious truth of the matter is that if public parks were considered to be traditional public forums for the purpose of erecting privately donated monuments," Alito said, "most parks would have little choice but to refuse all such donations."

Although the case was decided unanimously, four justices wrote separate concurrences to express individual concerns.

Justice David Souter did not join the majority opinion. Instead, he concurred in the judgment only. He said although he agreed with the outcome he had qualms about suggesting that public monuments are government speech categorically.

Justice Souter warned of potential difficulties ahead. "The interaction between the 'government speech doctrine' and establishment clause principles has not … begun to be worked out," he said. "The case shows that it may not be easy to work out."

In his own concurrence, Justice Antonin Scalia was less concerned about looming free speech and establishment clause clashes. In a two-page concurrence joined by Justice Clarence Thomas, he sought to reassure Pleasant Grove officials.

"The city ought not fear that today's victory has propelled it from the free speech clause frying pan into the establishment clause fire," he wrote. "There are very good reasons to be confident that the park displays do not violate any part of the First Amendment."