Fruit-flavoured tobacco is drawn through a hookah
The smoking ban needs updating to offer shisha bar owners clearer advice, Harrow Council in west London has said.
The bars, where herbal tobacco can be smoked through a communal pipe, tend to have an awning open to the street.
But the law on outdoor smoking shelters means those with roofs should be at least 50% open, so air can circulate.
And when cafes are fitted with low roofs and cushions to create a pleasant atmosphere, they can block ventilation and fall foul of the smoking ban.
One shisha cafe in Harrow has already been issued with a £200 fine.
Another settled out of court over breaches of the smoking ban rules.
As in any place of work, smoking is banned on the premises of all shisha bars, which are also known as hookah bars.
Councillor Susan Hall, Harrow's portfolio holder for the environment, said: "These cafes are becoming increasingly popular across London, but the legislation on smoking in public places wasn't framed with them in mind.
"It needs to be updated so all councils have clear guidance on what these cafe fittings should look like.
"We can then balance the right of customers to sit and enjoy the authentic shisha experience while continuing to deliver clean and safe streets."
Shisha bars, which are typically decked out with low stools and soft cushions to create an inviting atmosphere, are popular across London with both Middle Eastern customers and a young crowd.