THE HAGUE, July 1, 2008 (AFP) - A tobacco smoking ban came into force Tuesday in cafes, bars and restaurants throughout the Netherlands, with a uniquely Dutch exemption for marijuana smokers.

While patrons are no longer allowed to light up cigarettes, they can still smoke marijuana in the country's specially licensed 'coffee' shops as long as their joints contain no tobacco.

Many regular marijuana users prefer their weed rolled with tobacco and, as joint content is hardly the easiest regulation to police, some coffee shops have opted to switch their business to over-the-counter sales only, or to erect specially designated smoking areas.

At the Florence coffee shop in The Hague, a brand-new sticker took pride of place Tuesday on the counter over which marijuana and hashish is now sold in take-away fashion.

'Hospitable as usual, but smoke-free,' read the sign.

At the nearby Ceylon coffee shop, a handful of customers were enjoying their joints in a glass-partitioned smoking area separating them from the non-smoking sales kiosk.

As the law seeks to protect people from second-hand smoke inhalation, waiters are no longer allowed to serve their customers a cup of coffee inside the smoking room, so the owners put in a vending machine for nibbles and drinks.

'I think it is bullshit, especially in a coffee shop,' waitress Tjarda Breuer told AFP.

'People who come here do so to smoke, and people who work here know from the beginning that they will be working in a smoking environment. It is their own choice.'

The shop's manager, Monique Beyersbergen, said she expected an initial slump in business, but hoped things should get back to normal within a few weeks, 'once people get used to the new set-up'.

The Netherlands has permitted marijuana use in licensed cafes since 1976.

With the introduction of the smoking ban, it joins a growing list of European countries who have stamped down on the habit in public places for health reasons.

Leo van der Scheer, of the Engel Lunchroom in The Hague, said he was not too worried about business.

'The Dutch people are not so brave, they do what they are told,' he said.

'A lot of my clients are moaning about it, but they do it (adhere to the law). They may not like it, but they have no choice.'

People who wanted to smoke could still do so outside, and most restaurant clients would probably just smoke less, said van der Scheer.

'I already smoked 14 cigarettes less today than I would have ordinarily -- that is a good start. In the past many people walked out because the lunchroom was too smokey, now those people can return,' he said.

The hospitality industry had feared a patron exodus, with one poll suggesting more than half of owners were considering closing shop.

Unconvinced, a grouping under the banner 'Save the small horeca (hotel, restaurant, cafe) enterprise' lodged a legal challenge to the law that was heard in the district court in The Hague on Tuesday.

Judgment is expected Wednesday in the bid to exclude small enterprises from the smoking ban.

But as smokers fume at the legislation, their non-puffing counterparts are rubbing their hands in glee at the prospect of a night out in an unpolluted environment.

A study by Dutch healthcare research bureau Nivel recently found the hospitality sector could attract as many as 800,000 new clients among asthma sufferers and non-smokers.

The Food and Consumer Product Safety Authority said it had already started with inspections. Offenders face fines of up to 2,400 euros (3,800 dollars).

Special 'smoking evenings' were held at bars, restaurants and cafes around the country on Monday evening, with smokers put out on the street at midnight.

Less than a quarter of the Netherlands' 16-million population are smokers.