ESIDES a well-posted prohibition against smoking inside their Battery Park City home, there are a number of unwritten rules that govern the lives of Joseph Cherner, his partner, Laurent Seitz, and their two stunningly precocious daughters, Emma and Camille.

French is to be spoken at all times, DVD's must be in Spanish and vacations should be spent in luckless developing countries, preferably at the home of an impoverished local. Of course, some rules are made to be broken, and Camille, 9, violated at least one when she barged into an interview to announce, in English, that her father, head of the nation's largest antitobacco advocacy group, SmokeFree Educational Services, had once lighted up one of those awful things.

"But you didn't inhale, right?" she asked her father. Well, he explained, Daddy took one drag, gagged and then stamped it out.

Perched 32 floors above the Hudson River, the Cherner-Seitz household is the portrait of boundless wealth, familial bliss and, on this day, utter chaos. With four hours remaining until their departure for France, where they will all spend the coming school year, everyone was rushing around the six-bedroom apartment accompanied by a symphony of ringing telephones and the soundtrack from "Oklahoma!"

That is, everyone except Mr. Cherner, who was sitting at his desk as tranquil as a Buddha. After 15 years of fighting the tobacco industry through legislation, elementary school lectures and self-financed advertising campaigns, Mr. Cherner was savoring his greatest victory yet: the likely passage of a bill that would ban smoking in all New York City workplaces, including bars, restaurants and dance clubs. Although the City Council must still hold public hearings, the mayor, the Council speaker and six of the seven health committee members already back the bill, which would drastically alter the lives of an increasingly alienated constituency.

While Mr. Cherner's money and relentlessness helped bring about the disappearance of the cigarette vending machine, the end of the subway tobacco ad and the advent of mandatory nonsmoking sections in restaurants, the city's chief executive, Michael R. Bloomberg, has taken the initiative this time, proposing both a whopping cigarette tax and the sweeping legislation. "When the mayor raised New York City's excise tax and said, `I hope one day the revenues from this tax will go to zero,' I cried," Mr. Cherner said.

After years of being branded a millionaire kook by his opponents, Mr. Cherner, 44, finally feels vindicated. "All truth goes through three stages," he said. "It's ridiculed, then violently opposed and then accepted as self-evident."

With tobacco giants battling a national deluge of lawsuits and antismoking restrictions, it would seem that we are in the third stage.

It is not self-evident why an overachieving bond trader from suburban Washington would choose tobacco as his full-time nemesis. Except for a housekeeper who died of lung cancer, he never had a firsthand brush with the uglier side of smoking. In fact, the cause was chosen somewhat at random, he said. A childhood comic book habit left him with a superhero's mind-set about good versus evil. "To me it was the classic comic book fight," he said. "One side had all the morality and the other had all the money."

After struggling to pay for a master's at Columbia University, Mr. Cherner vowed he would one day become more like his role model, Spider-Man — that is, after he had made his first or second million. By 24, he had achieved that goal at Kidder, Peabody. He bought his parents a house, took a leave of absence and never went back to Wall Street.

One of his earliest forays into public life, in 1987, was a 30-minute lunch with Mayor Edward I. Koch that he said cost him $200,000. Mr. Cherner got to complain about tobacco ads at the city's stadiums and gave $100,000 to Mr. Koch's favorite charity. Mr. Cherner wound up spending another $100,000 for a public school contest that produced antismoking posters, some of which ended up on the city's subways. (The stadium ads eventually came down.) Mr. Koch later said the money had nothing to do with the decision to meet with Mr. Cherner.

HIS organization has no paid staff but can quickly inundate uncooperative elected officials with faxes and e-mail messages from its 105,000 members. Mr. Cherner's favorite ploy is to show up at public hearings with terminally ill cancer patients and cheerily introduce them to tobacco-industry lobbyists. Last year, his group helped convince Wal-Mart to remove giant cigarette displays from its checkout counters in Mexico. If he has his way, Wal-Mart stores in China will be next.

His dream? To see smoking banned at workplaces across the nation, even around the world. "The funny thing is, I'm not opposed to smoking," he said. "I support a person's right to smoke. I just oppose a person's right to make someone else sick."

Lest you think he is a one-issue guy, Mr. Cherner is also an advocate for mental health and gay rights (he and Mr. Seitz opened their home to a "20/20" camera crew two years ago).

While in France, Mr. Cherner will run the show by e-mail and phone, flying back to give testimony or speeches when necessary. And how will he cope with the French and their love affair with Gitanes? "I've got my list of smoke-free restaurants," he said. "And besides, even the French can change."