On a flawless Saturday, the lake-fed Rifle River runs clear and lively through the central Michigan outback. Warm breezes carry the heavenly scents of spring flora. The moment begs for a canoe and a voyage.

Provided, of course, the voyager doesn't mind company. Lots of it, in fact, hundreds of young people out on Memorial Day weekend in kayaks, rafts and canoes. And doesn't mind their consumption of libations, their public urination or their happy whoops. And doesn't mind the many-canoes-abreast parties or the guy standing in the shallow waters, holding a squirt gun with the caliber of a howitzer.

"You're too dry to be on this river!" he says, taking aim at a passing canoe whose occupants fervently wish to stay that way.

They don't.

It was on the Rifle, on a Saturday last August, that Timothy Joseph Boomer, of suburban Detroit, fell out of a canoe and into First Amendment history. Because after being deposited in the water, Boomer allegedly cut loose with f-related profanities, and a nearby Arenac County sheriff's deputy charged him with violating a 102-year-old Michigan law that makes it a misdemeanor to curse in the presence of women or children.

Since then, a tiny, rural county's evocation of Victorian mores has blossomed into a national sensation. Court TV wants to televise the trial of the 25-year-old defendant, a computer program writer in the auto industry. And when it begins on Thursday in the county seat of Standish, an American Civil Liberties Union lawyer will be at Boomer's side.

Noted but briefly amid the hoopla is why an officer of the law happened to be on the riverbank that day, on duty. Therein lies a tale of a different sort. It's not about freedom of speech. It's about having social graces in public places. It's about being able to float down a beautiful river without being subjected to X-rated language, young men relieving themselves or an unwanted dousing by super-soaker.

By last summer, government officials and canoe outfitters, fed up with "Animal House" behavior on summer weekends by a decided minority of visitors, had begun a campaign to impose some decorum on the river and in campgrounds by enforcing laws and pleading for restraint. Given the Constitution's guarantee of free speech, they might ultimately lose the Boomer case, but their civility crusade puts Arenac County not behind the times, but right in step with them.

There is mounting evidence that Americans think rudeness has overtaken politics, infested roads with rage, polluted airwaves, infected clerks and customers alike, made a family outing to a ballpark a lesson in bad language and made incessant chatter in movie theaters commonplace.

"The outside edge of human behavior gets farther and farther out in this country," said Lt. Alan Marble, of the Michigan Department of Natural Resources, whose officers now patrol the Rifle in kayaks on busy weekends, while sheriff's deputies patrol the shoreline.

Earlier this year, 190 members of Congress retreated to Hershey, Pa., for lessons in getting along, the second time they have done so. Johns Hopkins University has a project to examine the state of manners, and the University of California at Santa Barbara has one to explore incivility in political discourse.

Nearly nine of 10 respondents in a U.S. News & World Report poll in 1996 said boorish behavior is rampant. School officials across the Washington area have begun to crack down on student profanity and slurs, concerned they lead to violence and disrespect. Stadiums have set aside seating areas for families, so children won't have to hear what they now do.

P.M. Forni, a Johns Hopkins humanities professor who helped create the school's civility project, said Americans are realizing that "incivility has a direct impact on the quality of their lives." They have begun to connect "the small, everyday indignities with the larger issues, with the larger tragedies," like recent school shootings.

Lest the past be romanticized, Forni noted that in significant ways, society is more civil now. Treatment of minorities and women has improved. Young Americans, he said, "have developed more respect for people occupying lower positions in society."

But in a nation that worships individual rights, simple manners have come to be seen as "unduly repressive," a "bourgeois plot" and a vehicle to "thwart expression," Forni said. Too many people apparently cannot imagine how talking in a theater or changing lanes on a whim or swearing at an Orioles game might affect those around them.

Perhaps predictably, there has been a backlash against the backlash. In a review for Salon magazine of Yale law professor Stephen L. Carter's book "Civility," writer Beverly Gage suggested that the elite regularly worry about "the help" becoming unmannerly.

Beyond that, there's concern that denouncing offensive behavior and speech leads to Big Brotherism. An official of the Thomas Jefferson Center for the Protection of Free Expression in Charlottesville called Boomer's prosecution "an attempt to label a citizen a criminal because of government disapproval of specific words." The center even gave its annual "Muzzle Award" to Richard E. Vollbach Jr.

He's Boomer's prosecutor.

Vollbach responded by writing back to ask for something "suitable for framing," and he drolly noted in an interview that the ACLU has come after "rural Arenac County, with their old-time country principles that are archaic, that are not in touch with MTV, I guess."

Vollbach said that "of course" county residents -- there are 16,000 here, 135 miles north of Detroit -- use the very word Boomer is charged with using. "I can go days without hearing that word," he said. "And then I'll hear it. Maybe it's me who uses it." But, he said, "I don't do it when I know or should know there are children in the area."

Actually, profanity was not the top priority when authorities began dispatching officers to the river. According to Patricia Skarbek, the undersheriff, the scattered property owners along the Rifle, as well as campgrounds and visitors, had complained that some weekend voyagers were making love in public, cutting up picnic tables for firewood, littering, urinating, fighting. Ladd White, owner of the largest canoe livery on the Rifle, said almost every problem stemmed from too much drinking.

Judy Kelley, who owns a spectacular cabin on a bluff overlooking the river, recalled that years ago she used to hear canoeists and think they were having so much fun. Now, she said, "I hate them. I hate them."

"I don't see any of the canoeists down there respecting the beauty and the environment of that river," said Kelley, 58.

"They come here to have a party," said her husband, Ralph, 62.

Downstream, at the end of a 17-mile trip with buddies, Bill Plunkett stood at White's Canoe Livery, clutching a can of Michelob. "If you want to come here for a nice, somber trip down the river, this isn't the place, because it's pretty rowdy out there," said Plunkett, 25.

"People are just out to have a good time," said Jeff Cusmano, 21, who came from the Detroit area with about 40 friends for the Memorial Day weekend, one of the most crowded on the river. If canoeists encounter families, "we tone it down a whole lot," said Brian Beardsley, 20.

Tammy Smith said that's true. Usually.

Along with two of her children, Smith was the reason Boomer was charged. Taking an annual float trip with relatives, Smith, 32, was in a canoe with husband Michael, 32; daughter Samantha, then 2; and son Casey, 5. On earlier voyages, she said, young people on the river would spot the family coming and say, "Hey, cool it, guys. Don't throw your water balloons."

But on Saturday, Aug. 15, the Smiths came upon a man in the water "and he is mad, he is very upset," Tammy Smith said, and he was "using lots of profanity." She put her hands over Samantha's ears, she said, but there were no free hands for Casey's because her husband was trying to paddle away as fast as he could.

The family did not seek out the deputy, Tammy Smith said. He found them, asked what they had heard and took their names. They had no idea Boomer had been cited until weeks later but are glad he was.

"The First Amendment thing has nothing to do with it," Tammy Smith said by phone. "It's a common decency thing, to respect the people around you. . . . You just can't act like that, and if you do, you're going to have to understand that there are people around you who are going to be offended."

"I never knew she was there," Boomer said, and Tammy Smith agreed that Boomer did not seem to see them.

That day, the defendant was in a party of 10 in five canoes lashed together. He will not say what he yelled after his canoe hit a rock and he fell out. But Boomer, who has an 8-year-old son, did say he would apologize in person to the Smiths. He will not, however, plead guilty as charged. A conviction might trouble a potential employer, he said, and the case is "a violation of my freedom-of-speech rights."

His ACLU attorney, William L. Street, tried to have the anti-cursing law declared unconstitutional, but a judge ruled that Boomer's alleged words were not protected speech because there was "no discernible expression of thought, idea or concept." He did throw out the portion of the statute pertaining to women on the grounds that adults must be treated equally. But, he said in his opinion, "the First Amendment suffers no damage here by taking a backseat to the compelling interest in the morality of children."

Street disagrees, saying that "the mere actual or likely presence of a child" can become "a censorship device over speech that was intended to be from one adult to another adult." He would be offended to hear profanity on a river, he said, but the solution is to embarrass the user, not send him to jail for up to 90 days or fine him $100, which are the penalties Boomer faces.

"There are many, many things that occur in daily life that are highly impolite, bad manners that we do not want to criminalize and give everybody the right to call 911 and convert into a crime," Street said. "Part of what we all have to swallow is that . . . from time to time, I'm going to be offended by what people are going to force on me."

At trial, however, Street will not be able to refight whether the law should apply to children. The "most hotly contested" issue before the six-person jury will be whether Boomer knew or should have known children were nearby, Street said.

The attorney went out and "fly-fished the scene of the crime."

"It is wilderness," Street said, adding, "If you can't swear in the middle of the wilderness, where the heck can you?"

"You can swear in the wilderness," Vollbach said. "I don't think you can repeatedly scream the f-word in front of children. That is an area that was loaded with canoes. . . . There's people all along that river."

Until told otherwise, sheriff's deputies will continue to enforce the profanity statute, Sgt. Robert Beyerlein said. And by all accounts, the decorum campaign has improved weekends on the river dramatically. Ladd White, the livery operator, said matters would improve even more if there were a limit on how much beer canoeists could take with them.

He thinks six cans per person would be plenty.

CAPTION: Arenac County sheriff's deputies write up an underage member of a tubing party on Michigan's Rifle River for possession of alcohol.

CAPTION: Jamie J. Pomaville, 26, of Clarkston, Mich., soaks passing canoeists with a water gun on the Rifle River near Sterling, Mich.