MardiGrass to mull big issues after the bong throwing

After the competitive bong throwing, joint rolling and Growers Ironperson are over, participants at the Nimbin MardiGrass festival in northern NSW will get down to business.

Marijuana business, that is, and how "unjust" laws criminalising cannabis use must be scrapped.

"When I first started to practise law, prostitution was illegal," former magistrate and law expert critic David Heilpern told AAP.

"Blasphemy was illegal. Abortion was illegal, SP bookmaking was illegal, homosexuality and sodomy were all illegal and same-sex marriage was just an impossible dream. 

"Vagrancy, being homeless and penniless, was a crime. 

"None of those things are criminal anymore. Even euthanasia. 

"But if you smoke a joint you are guilty of a crime that can land you in prison for two years and a criminal record that can impact on your ability to work for the rest of your life." 

Mr Heilpern, who is dean of law at Southern Cross University, will be speaking on a panel on drug law reform on Sunday at MardiGrass, in northern NSW, along with federal Greens senator David Shoebridge.

The annual festival was first held in 1993 after multiple people were arrested and charged with possession and dealing marijuana in the small town, which has a strong counterculture history.

The Nimbin Hemp Embassy organised a protest march a couple of months later, and MardiGrass was born.

While the protest march is still the centrepiece of the festival which began on Friday, in the past 30 years it has grown to include workshops, a convoy of Kombi vans, entertainment and markets. 

There's also the Hemp Olympix, being held on Saturday, where participants compete in events like bong-throwing, joint rolling and the Growers Ironperson, which involves navigating a leach-infested lantana tunnel with a bag of fertiliser and bucket of water. 

One issue Mr Heilpern feels strongly about, after spending years presiding over courts in NSW regional areas, is drug driving laws. 

Under NSW law, it's an offence to have any trace of the psychoactive component of cannabis, tetrahydrocannabinol (THC), in your system while driving.

Unlike laws on driving under the influence of alcohol, people are tested for the presence of THC rather than the level of intoxication.

However, roadside saliva tests used in NSW can detect traces of cannabis for up to nine days after people have used it.

The federal government legalised the use of medicinal cannabis in 2016, but Mr Heilpern said during his time on the bench people were charged under drug driving laws despite being prescribed THC for chronic pain or anxiety.

"They would come to court and lose their licence and lose the ability to go to work, to take their kids to sport, all the things that we commonly drive to in regional areas," he said.

"And why? Because they were using medicine in accordance with their prescription without a solitary suggestion that they were adversely affected.

"And there were recreational drug users who are in the same boat, who days later would be apprehended and their lives would be turned upside down because of silly drug driving laws that mean people lose their licence or get a criminal record, all for something that causes no harm."

Mr Heilpern notes there has not been a single death "recorded by any coroner in Australia caused by someone medicinally using cannabis in accordance with their prescription."

In cases of possession, NSW has a cautioning system which means many people avoid court, unlike drug driving cases.

But the state still has the strictest possession laws in the country.