Lawmakers in the US city of San Francisco have voted to ban the sale of e-cigarettes.
It will apply to any products that have not received approval from federal regulators.
No such approvals have yet been granted, CNN reports.
While those backing the new law say it's an effort to cut down on e-cigarette use among young people, opponents suggest it will also hurt adults trying to quit smoking traditional tobacco products such as cigarettes.
Currently, US authorities say e-cigarettes must be regulated as tobacco products - but San Francisco officials claim that is not happening.
Earlier this year the Food and Drug Administration (FDA) set an August 2021 deadline for companies to submit their flavoured products for evaluation.
The new San Francisco rules, approved by lawmakers yesterday, will also impact some flavoured tobacco products.
However, it doesn't ban the use of the products by those aged 21 and older.
US media reports that city mayor London Breed has said she will sign the law, and the legislation is expected to be fully implemented by early 2020.
City Attorney Dennis Herrera said they were taking the action over what they believe is a failure by federal regulators to take action.
He argued: "This is a decisive step to help prevent another generation of San Francisco children from becoming addicted to nicotine.
"This temporary moratorium wouldn’t be necessary if the federal government had done its job."
He added: "E-cigarettes are a product that, by law, are not allowed on the market without FDA review.
"For some reason, the FDA has so far refused to follow the law. If the federal government is not going to act, San Francisco will."
The legislation specifically cites the high use of e-cigarette use among young people - suggesting the products are "frequently marketed in a variety of flavors with obvious appeal to youth, such as gummy bear, cotton candy, and fruit punch".
Figures suggest there are 3.6 million middle and high school students using e-cigarettes in the US.
San Francisco is notably home to the corporate headquarters of Juul Labs - the biggest e-cigarette manufacturer in the US.
In a statement reacting to the ban - quoted by NPR - Juul spokesman Ted Kwong said: "This full prohibition will drive former adult smokers who successfully switched to vapor products back to deadly cigarettes, deny the opportunity to switch for current adult smokers, and create a thriving black market instead of addressing the actual causes of underage access and use."
Meanwhile, the LA Times editorial board spoke out against the ban, writing: "Not only is it bad public policy to outlaw a legal product that’s widely available just outside the city’s borders, but it’s bad public health policy to come down harder on the lesser of two tobacco evils."
While San Francisco is the first major US city to ban the sale of e-cigarettes, a number of other countries - including Brazil and Singapore - have banned the products.