Jim Trulock and Julie Norris look like an average suburban Dallas couple. He's a graying middle-aged divorcé pushing 60. She's 30 years younger but partial to frumpy floral dresses. But on weekends their late-'70s split-level house in the southwestern Dallas suburb of Duncanville is transformed into "The Cherry Pit." Tubs of whipped cream are laid out with the chips and dip on the yellow Formica countertop. A garland of thong panties adorns a kitchen wall. After a game of Naked Twister or a turn under the disco ball, Jim and Julie and their most intimate friends might pile into their steamy oversize hot tub. And for the, ahem, climax of the night? A semiprivate romp in a side bedroom or a more gregarious encounter on white sheets in "the pit": a half-dozen beds pushed together in front of the fireplace.

Jim and Julie are swingers—couples who socialize sexually with other couples or singles living "the lifestyle," as they call it. Surprisingly, the Cherry Pit parties held in the Texan notch of the Bible Belt went relatively unnoticed for years, despite attendance of sometimes 100 or more invited guests. They stayed under the radar partly because the couple lives on a semisecluded, wooded one-acre lot near a state park, and partly because of the libertarian streak of many Texans. Despite the presence of a Boy Scouts campground across the street, they have few neighbors. But city officials said they had received dozens of complaints over the years that the "parties" on Cedar Ridge Drive were attracting streams of traffic to their normally quiet neighborhood. After examining the couple’s Web site, officials found a request for a suggested donation of $50 per couple (since removed) and accused Trulock of running a sex business from his home. In early November the Duncanville city council passed a law against sex clubs, calling them a public nuisance to the self-proclaimed family-friendly city.

The Cherry Pit parties continued, and Trulock was cited twice for the misdemeanor crime of operating a sex club. On Wednesday Trulock filed suit against the city, saying the new law is unconstitutional on the grounds that it invades the couple's privacy, denies them due process and is overly vague. "What they do behind closed doors, unless it's some kind of activity involving violence or children or animals or drugs, it's none of the government's business!" says their attorney, Edward Klein.

Trulock and Norris say they tried to be good neighbors. They had always set strict rules for their events: no drugs, no weapons and, above all, each guest's wishes must be respected by other guests at all times (in other words, "no" always means "no"). After the city "attacked," as Trulock put it in a message to the Cherry Pit's Yahoo online group, which has almost 4,000 members, they tried to keep the party going by encouraging car pools. When the city erected No Parking signs on the street in front of their driveway, they arranged for off-site parking. They toned down their Web site and tried to explain their lifestyle to the gawkers and TV camera crews that began cruising by their house. Bloggers joked that Baptists were trying to shut the swinger parties down because they might lead to dancing. Many of Trulock and Norris's neighbors told reporters they have a "live and let live" attitude toward what the couple does behind closed doors. But others denounced the swinging lifestyle. "It's immoral," says one neighbor, Jack Martin, a 74-year-old retiree. "Would you want someone living next to you who was a pedophile if you have a bunch of kids? It's on the same line. The frame of mind is the same. The end result is the same: sex."

Norris, a 29-year-old nonpracticing attorney with a law degree from Southern Methodist University, is cheerfully open about swinging, which she describes as a healthy and fulfilling lifestyle for couples. Their attorney has advised them to refrain from media interviews while their criminal case is pending, but she spoke briefly with NEWSWEEK. One common misconception about swingers, she says, is that they have troubled relationships. "Many people who are swingers believe that it saved their marriage. Now it's part of their marriage and part of who they are. But it has to be something you need or are interested in." While Norris and Trulock aren't married, many swingers are, she says. Other areas of the country are more open to the swinging lifestyle, Norris adds. But in Texas "the fear is if one little small town can do it, then everyone can."

No one knows how many swingers there are, but there is a growing number of Web sites, clubs and resorts that cater to the swinging lifestyle. Robert McGinley, founder and president of NASCA (informally known as the North America Swing Club Association), says many people "want more than just one bite of the apple." McGinley, now 74, became an activist for the swinging lifestyle almost 40 years ago with his wife. Today there are swinger clubs operating as public businesses or gatherings in private homes in almost every major city in America, he says. "In the United States we're rather uptight compared to all other Western countries when it comes to sexual behavior. But you cannot outlaw sex. You can try all you want to, but it won't stand up in life, even if it stands up in the courts. We are full-time sexual beings."

Swinging isn't new. California military families reportedly swapped wives at the first "key parties" in the 1950s; these events later became part of the lore of the swinging '60s and '70s. Today's modern swinging movement includes conventions and national publications—and Swing Stock, a four-day campout in the Minneapolis/St. Paul area featuring group showers and the crowning of a king and queen. Swingers even have their own generation gap; older swingers feel that the youth are too superficial or that they are looking for a "big orgy" instead of strengthening their current relationships and making new friendships, says Curtis Bergstrand, head of sociology at Bellarmine University, a Roman Catholic institution in Louisville, Ky.

The Cherry Pit started as a private gathering in an apartment in the 1980s in a neighborhood popular with young urban professionals. It outgrew those digs and eventually moved with its host to Duncanville. In 2004 Trulock and Norris restarted the parties, which compete for patrons of other Dallas-area swinger clubs, including the Silver Minx, Velvet Curtain, Spankee's Club, Iniquity and the Rustic Red House, to name a few.

The U.S. Supreme Court implied in a 1990 case involving the city of Dallas and sex businesses that commercial sexual activity does not constitute expression under the First Amendment. But Klein, the Cherry Pit's attorney, says Trulock and Norris's fight to protect the swinging lifestyle in the privacy of their own home is supported by a more recent Supreme Court decision, the 2003 Lawrence v. Texas case that struck down Texas's sodomy law. "That case is the seminal case about regulating private conduct," Klein says. "Any kind of private activity, [even] wearing pink socks in your home." A county judge denied Klein's motion Wednesday for a restraining order against the Duncanville law. Now they'll try for an injunction while the lawsuit works its way through the courts—a process that could take a decade or longer. City officials, declining to comment further, issued a statement saying they will respond to the lawsuit in court and continue to enforce the sex club law.

Officials in Duncanville and other cities that have tried to limit swing club activity have said they're not trying to outlaw sex or cast judgment on private activities. Instead they style their efforts on the need to curtail noise and traffic in residential areas and control commercial sex activity. But Trulock and Norris claim that the Cherry Pit isn't a business. Klein likens their gatherings to Super Bowl parties. "If I invite a bunch of people over to my house to watch the Super Bowl and I provide the refreshments and I ask them for 10 bucks to defray the costs, it's just like this. It's just that the activity that goes on isn't watching the Super Bowl," he says.

Klein describes himself as a "wide-eyed liberal" with a weakness for personal freedom causes. When he was a "baby lawyer" his former firm helped defend Hustler magazine and argued against drug paraphernalia laws. He says he's not a swinger and never plans to be. "To me it was like discovering a tribe of people in some remote area of the world that you had no idea existed, with their own hierarchy, their own social rules, their own code of conduct."

A 2000 study of 1,200 self-professed swingers found a cross-section of respectable America. "They're not that odd. They are Middle America: they're doctors, they're lawyers, they're school teachers," says Bellarmine University's Bergstrand, who co-authored the report. "It doesn't mean that swinging isn't a disaster for a lot of people, because it is," he concedes, adding that the practice isn't something he or his wife is interested in.

One thirtysomething advertising manager who asked to remain anonymous remembers her boyfriend taking her to the Sans Souci swinging club in Dallas a decade ago. They were five years into a seven-year relationship, and the thrill had worn off. "It was like a secret society revealed," she says. "It looked like a lot of older couples who had been married for 20 years and were bored, so they wanted to try an open marriage." Her boyfriend found it "exciting and fun," but she was "annoyed" by women hitting on her and jealous of her partner's outside attentions. After several arguments they never returned. "I didn't want him or me to be involved in that lifestyle."

While the legal battle continues in Duncanville, so do the parties at the Cherry Pit. Trulock and Norris have raised a few thousand dollars so far for their legal fight, but they'll probably need more if the case drags on. If only their private gatherings had stayed under the covers.