Smoking dope is the raison d'être of the cafes which are scattered across the country, with the greatest and most famous concentration in Amsterdam. But when the tobacco ban comes in, the coffee shops will not be exempt.

This will lead to the paradoxical situation that only pure grass or cannabis resin, which are not covered by the ban, can be legally smoked in the shops.

Anybody rolling a tobacco-based joint will be breaking the law – but only because of the tobacco. "The new rule is nonsense," said Willem Panders, of the Dutch tobacco traders' union. "It will be almost impossible to enforce because how are you going to check if someone is smoking cannabis mixed with tobacco, or pure cannabis?"

But despite desperate lobbying, owners have failed to get the government to make an exception of them. "Coffee shops will be treated in the same manner as other catering businesses," the Prime Minister, Jan Peter Balkanende, said last week. "It would have been wrong to move towards a smoke-free catering industry and then make an exception for coffee shops. People would not have understood that."

At any one time up to 1,300 coffee shops are for sale across the country, but the Dutch catering magazine Horeca Vizier reports that the figure has jumped to 1,600 because of the ban.

Marc Jacobsen, of BCD, a national association of coffee-shop owners which has been urging the government to give them special status, told the online version of Der Spiegel: "In a cafe you come to drink something. In a restaurant you come to eat. But when you come to a coffee shop you come to smoke, so smoking has to be allowed in a coffee shop."

As in the rest of Europe the purpose of the ban is to protect the health of staff, who at present are obliged to inhale passively other people's smoke. But Sandy Lambrecht, the manager of the Bulldog coffee shop on the Leidseplein in the heart of Amsterdam, said: "The new rules are absurd. You come to a coffee shop to smoke, after all – it's ridiculous that we have to comply. The new rules are meant to protect employees like me, but the point is that we chose to work here."

Paul Wilhelm, the owner of De Tweede Kamer, one of Amsterdam's most famous coffee shops, founded in 1985, argued: "If the boys are old enough to be sent to Afghanistan, then you can't tell me that people want to protect them from smoke in the workplace. They're old enough to decide on their own. They can vote, they can go to war – but now they won't even be allowed to make this decision?"

Many British pubs re-opened their gardens when the smoking ban took effect, but most Dutch coffee shops are penned into tiny premises with no outdoor space. The solution in Bulldog is to create a separate, walled-off space for those who want to smoke, off-limits to staff.

"We're now having to build a new section in our coffee-shop with a glass partition and special air filters for those who choose to smoke non-pure cannabis," said Sandy Lambrecht. "It's a shame as it will change the very congenial ambience in here – half of our customers will be shut off behind a glass wall. Our customers will grumble, that's for sure."

But the Dutch Health Minister, Ab Klink, is impenitent. "A positive side effect of the smoking ban," he said, "may be that consumers who spend the whole day hanging out in coffee shops will find other things to do."

Cannabis cafe culture

Contrary to popular perception, cannabis is – technically – an illegal substance in the Netherlands. However the country's pragmatic drug policy has led to a division in the eyes of the law between "hard" drugs, such as cocaine or heroin, and "soft", like cannabis.

Holland's policy of non-enforcement towards cannabis consumption and possession goes back to 1976. Originally it applied to a quantity of less than 30 grams, but the amount coffee shops are able to sell to one person is now limited to five grams.

Cannabis cafes haveto stick to strict criteria. They must be licensed, cannot admit or sell drugs to minors under 18, and the advertisement of drugs is banned. In April 2007, new legislation forced the coffee shops to choose between serving alcohol and cannabis. The vast majority opted to serve cannabis.

Although cannabis is usually mixed with tobacco and smoked in a joint, it can be smoked – without tobacco – in a bong or pipe. It can also be consumed as a tea or in cake form, but the effect of the drug takes much longer to be felt.