New South Wales police have recently been denying fans entry to gigs even when they do not find any drugs on them.

But at a press conference this morning, Chief Inspector Gary Cowan said police will not be taking this tough new approach at Splendour in the Grass.

The three-day festival at Byron kicks off on Friday with tens of thousands expected to attend. There will also be hundreds of police, Chief Inspector Cowan warned this morning.

"If you want to bring drugs onto the site rest assured if you get detected with drugs you'll have your ticket ripped up and you won't be coming to the event," he said.

Asked what he meant by 'detecting' - whether it meant police finding drugs or just the dog sitting down - the Chief Inspector answered: "No, finding them."

"You actually have to have drugs on you for us to take any action."

That wasn't the strategy at State of Trance in April, Midnight Mafia in May, and Above & Beyond in June, where police kicked out punters despite searching them and not finding drugs. Police said sniffer dogs could "detect the presence of prohibited drugs or someone who has recently had drugs on them" and the dog sitting down was reason enough to deny entry.

Studies show that sniffer dogs sitting down next to a person is not a good indicator that person has drugs. Over a decade of NSW Police data shows the dogs have gotten it wrong (made a false positive) between two-thirds and three-quarters of the time.

At the Midnight Mafia gig alone, police denied entry to 150 people who were searched and did not have drugs.

Some punters who were kicked out have threatened to sue police.