A man found to be selling electronic cigarettes on the Internet has been fined by a Danish court, paving way for a similar crackdown on hundreds of other retailers.
Under a 2008 directive from Denmark's health authority, e-cigarettes are a pharmaceutical product requiring formal approval before they are sold.
The rules had never been formally tested until a man was taken to court in the eastern town of Randers after ignoring repeated warnings from the health authority.
In January the authority said it had reported 25 people to the police for selling e-cigarettes illegally.
The man was fined 50,000 kroner (6,700 euros, $9,300) -- setting a precedent in a country where 200,000 people use e-cigarettes and around 200 outlets sell them, none of which have been formally approved by the government yet.
"All medical drugs in Denmark have to be approved by the Health and Medicines Authority," prosecutor Peter Koukoumis told AFP.
"So far nobody has applied to sell e-cigarettes as a medical drug, so if someone is selling them it's illegal," he added.
The product is in the same category as nicotine patches and chewing gums, which are both regulated by the agency, in that "its sole purpose is to provide the user with nicotine," he said.
E-cigarettes are battery-operated devices that deliver vaporised nicotine into an aerosol inhaled by the user.
Governments around the world have been moving to regulate e-cigarettes amid uncertainty about their health effects.
Last week, US regulators proposed their first restrictions on the soaring $2 billion (1.4 billion euro) market, including requiring sellers to enforce a minimum age restriction on those who wish to buy e-cigarettes.