San Francisco has become the first US city to ban sales of e-cigarettes until their health effects are clearer.
Officials voted to ban stores selling the vaporisers and made it illegal for online retailers to deliver to addresses in the city.
The law is set to come into force in February next year, but there have been reports that firms could mount a legal challenge.
Anti-vaping activists say young people are being deliberately targeted, by offering flavoured products.
While critics of e-cigarettes say more evidence is needed on the impact and claim that vaping can encourage young people to switch to cigarettes.
Juul Labs, the most popular e-cigarette producer in the US, said the move would drive smokers back to cigarettes and “create a thriving black market”.
Earlier this year, the US Food and Drug Administration issued proposed guidelines giving companies until 2021 to apply to have their e-cigarette products evaluated.
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