LONDON -- Undeniably, investors in British American Tobacco (LSE:BATS) have had a good run. Over the past 10 years, the company's shares have risen 460%, handsomely outperforming the FTSE 100's more modest 67% growth over the same period.

And if this weren't enough, it has also pleased income investors. A perennial favorite with dividend seekers, British American Tobacco has consistently offered a yield a shade below 5%.

In short, it's been a "have your cake and eat it" sort of company, offering an enviable total return. And as with fellow "sin stock" Diageo, it's difficult to escape the conclusion that the folks who bank on booze and baccy have been right all along.

Even so, I've never bought in myself, querying the logic of owning a stake in a business where the products that it sells kill those who consume them.

But if I did hold British American Tobacco, I might today be thinking of selling. Because the company's recent results may be signalling that cigarette manufacture has gone ex-growth.

All change
Of course, people have been saying that cigarette manufacturing ought to go ex-growth for years. But there are now signs that the drip, drip, drip effect of high taxation combined with anti-smoking legislation might be having an effect.

Just yesterday, for instance, Ireland -- one of the first countries in the world to ban smoking in pubs, restaurants, and workplaces, back in 2004 -- followed Australia and mandated that tobacco firms only sell cigarettes in plain, non‑branded packaging.

Here in the U.K., legislation that came into effect last year requires all large shops and supermarkets in England to cover up cigarettes, and hide tobacco products from public view.

Around the world, in short, selling tobacco is becoming an increasingly tough proposition -- and sure enough, British American Tobacco's results highlight falling sales.

Declining volumes
For me, one of the most striking things about British American Tobacco's full year results for 2012 -- apart from the slowing rate of dividend increases -- was the statistic that overall cigarette volumes were down 1.6%. This was "mainly due to contractions in some of our larger markets," said the company.

And look at the latest trading statement, released on April 24, and the same thing can be seen again: overall volume down 3.6%, with a rise in Asia Pacific of 6.7% partly masking falls of 10.3% in Western Europe, 1.8% in Eastern Europe and Middle East, and 15.6% in the Americas.

In other words, the rising revenues that have propelled British American Tobacco's resurgent share price and earnings look to be under threat. For the financial year ending Dec. 31, 2012, for instance, reported revenues were down 1%, with only its revenues at constant exchange rates showing a rise of 4%.

So is it time to sell -- and put the proceeds to work elsewhere, in a share with better long-term prospects? Had I got a stake in British American Tobacco, I suspect that I'd be asking that question. A temporary hiccup is one thing -- I view them as potential buying opportunities -- but long-term decline is another.

Follow the money
Of course, whether this recent decline in volume at British American Tobacco makes the business a "sell" is something that only you can decide.

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Malcolm Wheatley has no position in any stocks mentioned. The Motley Fool recommends Diageo. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.