That's what happened to Scott Rodrigues of Massachusetts, and he is suing the Scotts lawncare company for violating his privacy and civil rights.
"It's a freedom thing: 90 percent of Americans support me and in Europe it's more like 100 percent," said Rodrigues, who claims that since he was fired last year he has featured in newspaper articles in Britain and appeared on radio shows in Poland and Lithuania.
A poll published last week showed that most Americans think Rodrigues's firing was unfair. Only seven percent of Americans think employers should be allowed to sack workers who smoke, the survey said.
Rodrigues says Scotts told him when he was hired that they were trying to become a non-smoking company.
According to the 31-year-old who has a licence to apply pesticides, he cut back with the help of nicotine substitutes from a pack to around five cigarettes a day within a few months.
But he was fired around six months after joining Scotts after a test showed he had high levels of nicotine in his blood.
"On the way to the test, I was chewing Nicorette gum. I pointed that out when they told me I had 'extremely high' levels of nicotine in my blood," Rodrigues said.
"A urine analysis will give a positive result for nicotine if you're chewing nicotine gum," Marion Adler, a doctor specializing in smoking cessation at France's Beclerc hospital near Paris, told AFP.
"You can also do a very easy test for carbon monoxide. If you smoke, it will be positive, if you don't, it won't," she said.
A spokeswoman for Scotts was unable to give details about the test given to Rodrigues or to comment on his case, only saying it was part of a company policy to promote a healthy lifestyle among its workers.
Scotts has built a five-million dollar wellness facility at its Ohio corporate headquarters and gives employees help in quitting smoking, losing weight or other health-improvement schemes.
"What we are doing is trying to give associates tools to live a healthier lifestyle," she said.
Oncologist Frank Settipani said companies who ban smoking and then test for nicotine were sending out a mixed message.
"What they seem to want is for people to stop putting smoke in their lungs, but if they're testing for nicotine, then what that says is we want you to quit nicotine, which is as addictive as cocaine, heroin or alcohol," he said.
"If the policy is no smoking, not no nicotine, then there are plenty of smokeless forms of getting your nicotine - pills, chewing gum, patches," he said.
"Cigarettes should be outlawed," he added.
"You should not be able to get nicotine by such a terrible delivery system -- inhaling burning leaves," said Settipani, who estimates that one-third of his patients at the Colorado-based Rocky Mountain Cancer clinic have smoking-related illnesses.
Meritain, the largest independent provider of services for self-funded health plans in the United States, is another company with a no-tobacco policy.
Employees at Meritain's Michigan branch can be suspended without pay and have been fired for violating the tobacco policy.
Ed Sweda, a Boston-based anti-tobacco lawyer, said Massachusetts and Michigan are among some 20 states without so-called smoker protection laws, which were pushed through by big tobacco in the 1980s.
Without smoker protection laws on a state's statute books, firms can discriminate against and even fire smokers "regardless of how right that is or how popular," Sweda said.
Most companies crack down on tobacco to cut healthcare costs and create a healthier working environment, Sweda said.
But although an ardent campaigner against tobacco, he condemned firms that "cavalierly say 'go find another job if you don't like our policy.'"
"We have to recognise how powerful the addiction is to nicotine and that it really is difficult to quit," said the senior attorney for the Tobacco Control Resource Center.
"I would want a company that is considering doing this to have mechanisms to assist smokers who are making genuine, good-faith efforts to quit," he said.
Rodrigues, meanwhile, has a new job.
"I work for the competition," he said. "They called me and said, 'We don't care if you smoke. We know you do a good job.'"