Starting July 1, the Netherlands will banish tobacco smoke from restaurants and all other public places. But patrons of certain coffee shops where marijuana is sold over the counter can still light up their joints.

Possessing the weed is actually illegal in the Netherlands, but smoking it is tolerated.

Carol Pucci/Seattle Times (ENLARGE)

Some Amsterdam business owners argue that the city's renowned coffee shops -- where marijuana is smoked openly -- are one of the main reasons why so many tourists visit.

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Shop owners say the tobacco ban — a trend that is becoming increasingly widespread in Europe — could be a threat to the specially licensed coffee houses, because patrons traditionally prefer their marijuana joints mixed with tobacco.

"As this is a ban on tobacco smoke, most coffee shops will allow customers to smoke pure weed, but not tobacco, and this will be potentially really difficult to regulate," said Lorna Clay, manager of the Cannabis College in Amsterdam, a nonprofit organization that distributes information about marijuana usage.

"Will the staff have to watch people make their joints to be sure no tobacco has been used?" she asked.

Clay said some of Amsterdam's 226 coffee shops have invested in new kinds of pipes and vaporizers to encourage pure cannabis use.

But she said other coffee house owners have no intention of stopping customers from smoking mixed joints.

These owners argue that the city's renowned coffee shops are one of the main reasons why so many tourists visit.

The new law comes on the heels of another change in what's thought to be a major Dutch tourist draw — legalized prostitution.

The sex trade is regulated and is mostly confined to red-light districts.

City officials announced last year that they would tighten rules in an effort to stop money laundering and trafficking in women.

Officials began shutting the famous brothels that display lingerie-clad women in shopfront windows, and today there are 400 window brothels, down from 478 last year.

"This is an attempt to stop criminal activity," said Bas Bruijn, a spokesman for the city of Amsterdam. "This is not an effort to end prostitution at all."