It is just one short stretch of road - 220 yards long - and until recently a little-known stretch too. It has turned into a battleground over two of Americans' most cherished rights: freedom of speech and freedom of religion, both enshrined in the first amendment to the constitution. Unfortunately, they are not necessarily compatible.
This is Main Street in Salt Lake City, capital of Utah, the heartland and headquarters of the Mormons, or as they prefer to be called, the Latter-day Saints (LDS). The Mormons founded Utah , and dominate the state. Opponents say the row over Main Street is just the latest example of their ruthless determination to have total control of the place. The church says it just wants the respect people would give any other religion.
The city sold the road to the church for $8m (£4.98m) four years ago. The traffic has been diverted, the area handsomely landscaped and the public given an "easement" to protect pedestrian access. The problem is over what that easement actually means. The public suddenly found Mormon rules now apply on this stretch of Main Street : no smoking, no sunbathing - and certainly no criticism of the church.
This has turned into a legal fight that may go all the way to the supreme court. The appeals court has just ruled against the church, and decreed that it cannot stop people protesting.
The stretch in question is at the very end of Main Street , linking the city's chief shopping and transport artery with its main tourist attraction: the Mormon Temple . Even though non-believers are never allowed to view the temple's innards, they still find it jaw-droppingly awesome, combining as it does something of Westminster Abbey, a Transylvanian castle and a Stalinist block of flats.
Even some of the Mormons' bitterest opponents in Salt Lake City - and there are a good many - have a little sympathy with them on this. Most admit this was never a traditional site for protest, and that the people now taking advantage of it are not rational critics. They are what the Salt Lake Tribune called the "harass-a-Mormon-for-Jesus-crowd" - Protestant fundamentalists who make a habit of standing close to LDS gatherings, such as wedding parties, and shouting abuse.
"It is a perfect illustration of what we were fearful of all along," said Mike Otterson, the church spokesman. "These are not people handing out pamphlets. They say the most horrible things. We've had brides in tears because of them. It's a violation of common decency."
Even John Saltas, editor of the city's alternative paper, the Salt Lake Weekly, agrees with that: "The protesters are just jerks with bullhorns."
But many Utahns see this dispute in symbolic terms: an illustration of the church's determination to impose its rigid value systems on non-believers. Utah is growing fast, partly because Mormons, with church encouragement, produce phenomenal numbers of children (10 or 12 is routine) and partly because outsiders see it as an attractive place to live.
However, incomers are often shocked by what they see as the church's control-freakery. LDS members are expected to avoid alcohol, tobacco, tea, coffee and any kind of sexual display, and away from the cosmopolitan state capital, non-conformists can find life difficult: the licensing laws are restrictive, bordering on bizarre.
Salt Lake City itself now has a slender non-Mormon majority but nearly all the leading politicians are believers, and many outsiders regard the local Republican party, which dominates the state's politics, as simply the church away from prayer.
"It's like the Taliban," Mr Saltas said. "There is this complete vilification of anyone who opposes them. It changed last year when everyone was here for the Winter Olympics. Now it's back to normal. When something like this happens, everyone else just gets pushed out of their way."
"In reality, Utah is a theocracy," said Janelle Eurick, staff attorney for the Utah branch of the American Civil Liberties Union, which is fighting the church in court over this case. "A lot of people are moving here with divergent viewpoints and the LDS is going to have to adapt to that."
Mr Otterson is aggrieved, partly because the land deal was not even the church's idea: he says city planners first proposed the deal about 40 years ago, and it was reactivated when the city sold the church the underground rights to the land to build a car park for the huge new Mormon convention centre.
"We are not contesting the right to protest," Mr Otterson insisted. "But when people go to the Vatican they are respectful. This property is next to our most famous icon. Is it too much to ask that people behave respectfully?"
The man in the middle of all this is the mayor of Salt Lake City, Rocky Anderson. Mr Anderson, a lapsed Mormon and a liberal Democrat, has offered a compromise whereby the city would give up the Main Street easement in return for the church handing over land in a disadvantaged part of town and funding a new youth centre.
The church is sympathetic to the compromise; opponents are more sceptical. Mr Anderson somehow has to keep both sides happy, which in Utah seems impossible. At a recent meeting, he had to be given an armed guard. It was not immediately obvious which side might have attacked him. It could have been either.
The Church of Jesus Christ of Latter-day Saints is said to be the fastest-growing in the world, with more than 11 million members, including 180,000 in Britain. It began in 1830 after a farmer's boy from New England, Joseph Smith, claimed to have received a divine revelation and golden tablets which showed that the 10 lost tribes of Israel settled in America before the birth of Christ. The result was the Book of Mormon.
Smith began to gather followers who trekked west as they established their own church, and a good many enemies, and in 1844 he was killed by a mob in Ohio. But a new leader, Brigham Young, led the Mormons west to find a new home in Utah, where they grew and prospered.
The early Mormons practised polygamy, which was one factor in their unpopularity, but a further divine revelation led it to being banned so that Utah could achieve statehood in 1890.
A few polygamists remain in remote rural areas, but the church now encourages large monogamous families. Birth control and abortion are barred, along with alcohol, tobacco, drugs, homosexuality, pornography - and tea and coffee. Members are expected to tithe a tenth of their income, making the LDS church very rich as well as locally powerful.
Mormons are expected to spend two years on missionary work anywhere they are sent, and 60,000 clean, polite and chaste young people are always knocking on doors across the world.