The Cancer Council wants WA's tobacco laws changed to specifically ban electronic cigarettes after a test case that sought to charge a business for selling them was thrown out of court.

Joondalup Magistrate's Court ruled last week there was not enough evidence that two types of electronic cigarettes looked like cigarettes or cigars, acquitting the operators of Heavenly Vapours of breaching the Tobacco Products Control Act.

So-called e-cigarettes are battery-powered devices that do not burn tobacco but turn nicotine or fruit flavours into vapour that is inhaled and exhaled.

It is illegal to sell e-cigarettes that contain nicotine under Australian law.

The WA Health Department prosecuted the Duncraig-based operators who sold e-cigarettes and nicotine-free "e-juice" through a website in late 2011.

WA tobacco laws prohibit the sale of any food, toy or other product that is not a tobacco product but is designed to resemble a tobacco product.

But the court ruled the electronic cigarettes did not necessarily resemble a cigarette or cigar and could also look like a fountain pen. Unlike normal cigarettes, they also required the user to press a button.

Cancer Council WA director of education and research Terry Slevin said it was a legal loophole that needed to be fixed because electronic cigarettes were a growing concern.

Data from the Centres for Disease Control and Prevention in the US recently showed the number of middle and high school students who used e-cigarettes more than doubled from 2011 to 2012.

Mr Slevin said the Tobacco Products Control Act was due for a review and could help ban e-cigarettes as well as address issues such as the need to reduce the number of licensed tobacco retailers.

"This incident of a failed attempt to prosecute points to the fact that the current provisions are not adequate," he said.