A constitutional challenge of Canada's new medical marijuana laws got underway Monday morning in Federal Court in Vancouver.

The case centres on whether patients can grow their own pot for medicinal purposes.

Last April new federal marijuana laws banned all home growing for medical purposes, meaning users would have to buy pot from licensed growers.

But four patients who grow their own marijuana challenged the new regulations in court, arguing licensed producers will inflate the price, making medical marijuana too costly.

The court heard testimony from Shawn Davey, who uses medical marijuana to alleviate chronic pain.

His lawyer John Conroy argued the new laws force patients like Davey to choose between liberty and health.

The federal lawyer said he'll prove the constitutionality of the current laws.

Back in March, lawyers for the patients won a temporary injunction allowing patients to continue cultivating their own marijuana, until the case is finally decided.

In December the federal government lost an appeal to strike down that injunction.

'We need this victory'

Meanwhile, Canada's self-proclaimed "Prince of Pot", marijuana advocate, Marc Emery, was among the supporters at the case.

Emery was released from a U.S. prison last year after serving four years for selling marijuana seeds to American clients from his Vancouver-based store.

"We need this victory and we need people to be able to grow their own medical marijuana," said Emery.

The trial is scheduled for up to three weeks.

Other challenges underway

The federal government's new regulations are also facing legal challenges from at least one company that failed to get licensed under the new program.

Since the new rules came in, at least 15 operations have been licensed to sell medical cannabis.

At least 13,000 patients have registered with the new licensed producers. Prices range from as low as $2.50 a gram to as high as $15, though most are between $8 and $10.

Health Canada says it does not know how many patients continue to grow their own marijuana because of the injunction.

With files from Farrah Merali, Bal Brach and The Canadian Press