When is a monument a cultural display — and when a religious statement?

When is a city free to accept a gift with a distinct message — and when can it say, "Thanks, but no thanks"?

The text of the First Amendment might start with "Congress shall make no law respecting an establishment of religion . . . or abridging the freedom of speech." But those words sound a lot clearer than the law turns out to be in practice.

Take the case of Pleasant Grove City, Utah, v. Summum.

Summum, a sect that started in Utah in 1975, holds that the Ten Commandments were, in essence, the second draft of God’s law that Moses brought down from Mount Sinai. Summum believe that the original version contained Seven Aphorisms: psychokinesis, correspondence, vibration, opposition, rhythm, cause and effect, and gender.

Not surprisingly, when Summum founder Corky Ra in 2003 asked to put an aphorisms monument in Pleasant Grove’s Pioneer Park, the mayor said "no."

Other items in the park — a mill stone, a water well, the first city hall — are historically significant and closely connected to the community.

But there’s also a large granite Ten Commandments donated by the Fraternal Order of Eagles in 1971.

It’s just like the tablets the Eagles gave Texas in 1961 to promote good moral character among youth along with movie director Cecil B. DeMille’s epic The Ten Commandments.

So Ra sued Pleasant Grove, arguing that officials couldn’t give park space only to messages they like.

He died in January and has been mummified. But the litigation continued, resulting in some lively arguments a week ago as the U.S. Supreme Court looked for an intersection between the First Amendment and common sense.

When is a park like a museum?

Is a monument like a parade?

Could the government, if it wanted, exclude the names of homosexual soldiers from the Vietnam Memorial?

If we have a Statue of Liberty on public property, must we have a statue of despotism?

Can a city put up a sign in the playground saying "clean your plate" but refuse a sign that says "pull the dog’s tail"?

(Read the transcript: http://tinyurl.com/parkdisplays)

At heart, the dispute is about whether the government can pick and choose among religious monuments that get to use outdoor public spaces.

It would be complicated enough if this were like the cases in which the court has said nativity scenes and menorahs can be displayed in public parks — if they’re surrounded by enough elf-hatted garden gnomes hoisting candy canes.

But the Summum haven’t claimed religious discrimination; they’ve made it about free speech.

Public parks traditionally are considered public forums where the government can set content-neutral limits, such as requiring a permit to hold a concert, but must let anyone with something to say speak.

A message can get shut out only for a compelling reason, such as a threat to public safety.

But if that’s the framework that applies to this case, then Pleasant Grove is wrong and everyone who wants to, including the Summum, can clutter Pioneer Park with monuments.

Lawyers for Pleasant Grove argued that the Ten Commandments monument stopped being the Eagles’ message and became the city’s message, and the First Amendment puts no restrictions whatsoever on what the government can say.

But if there aren’t rules for government speech, it could unreasonably limit the names inscribed on a war memorial. The government could, as a lawyer for the Bush administration argued, take a monument that’s donated by a private group and "move it, modify it, destroy it, drop it to the bottom of the ocean, sell it on eBay."

And if the city of Pleasant Grove endorses the Ten Commandments, how does that not amount to promotion of one religion over others, a violation of the First Amendment’s establishment clause?

The justices dodged that problem three years ago with Texas’ Ten Commandments monument, which sits along with 16 other memorials on the state Capitol grounds. Passive display with moral and historical significance, therefore acceptable, the court concluded.

Justice Stephen Breyer provided the crucial fifth vote in that case, which was decided before Chief Justice John Roberts and Justice Samuel Alito joined the court.