India banned smoking in public places on Thursday in an attempt to fight tobacco use blamed, directly or indirectly, for a fifth of all deaths in the world's third-largest consumer.
The ban, which includes all offices and restaurants, will hit its estimated 240 million tobacco users, who are likely to find their homes and cars among the last few places to light up.
The government cites the economic costs and the need to stem the loss of human lives but tobacco firms say the ban infringes on individual rights.
Everyone agrees, though, that implementing the ban could be a problem and much will depend on compliance rather than enforcement.
The ban includes schools and colleges, pubs and discotheques, hospitals and bus stops. Offenders will be fined 200 rupees ($4).
"Don't wait for enforcing authorities to catch you," said Anbumani Ramadoss, India's health minister who has long championed a ban on tobacco, urging Bollywood actors not to encourage smoking by lighting up on screen.
Past attempts to ban spitting and urinating in public in India drew little success, and the impoverished and lawless northern state of Bihar has already expressed reservations about the practicalities of implementing the ban.
While rules limiting advertising, marketing and sales existed before, implementation was not very effective.
Not everyone is happy with the ban. Many say a lack of smoking rooms mean they would be deprived of a stress-busting puff in offices and other public places.
"The intention may be good, but are we a nanny state?" asked Sanjay Yadav, a furtive puffer on a New Delhi road. He said the ban could be an incentive for those smokers wanting to quit.
Rajesh Kumar, a tobacco products seller, says he did not expect sales to drop. "Smokers will smoke," he said, adding he hoped to continue selling about 50 packets a day he sold now.
Official figures say that with its 240 million tobacco users India has annual cigarette sales of about 102 billion sticks.
But that is still a small market compared to China's, where, says WHO, one of every three cigarettes in the world is smoked.
With cigarette sales growing at an average annual rate of about 5-6 percent, ICICI Securities estimates, India is one of the few world markets to show growth in cigarette consumption.
So, much is at stake for India's top cigarette maker, ITC Ltd, which has challenged the ban in court.
The case is scheduled to come up in Supreme Court on November 18, an ITC spokesman said.
ITC, which also has interests in apparel, software and paperboard, has been pushing into packaged foods and personal care products as it seeks to cut its reliance on cigarettes.
Still, cigarettes make up a lion's share of its profits, with the new initiatives expected to contribute only gradually.
With the ban, India follows countries such as Britain, France, South Africa and Thailand.
Worldwide, more than five million people die of tobacco related illnesses now.
This, the WHO says, will rise to more than eight million in the next 20 years, most of them coming from low and middle income countries such as India.