Police have seized 10kg of suspected synthetic cannabis and $100,000 cash in a raid on Rockingham retailer Pipe Dreams.
A 41-year-old Orelia man was arrested at the shop and police allegedly found cannabis and smoking paraphernalia during a later search of his house.
No charges have been laid because police are yet to test the seized substances.
The possession, sale and supply of synthetic cannabis is illegal in WA.
The search warrant was executed after Upper House MP Phil Edman last month instructed a staffer prove how easily accessible synthetic drugs were to purchase.
Mr Edman was outraged the staffer was able to easily buy synthetic cannabis at Pipe Dreams and another Rockingham retailer.
He said he was glad authorities had acted on the issue.
“I have been watching the store before it opens in the morning and there’s generally about 20 people going in at about 9am to get their stash,” he said.
Mr Edman said the State Government needed to take a stronger stance on synthetic drugs and retailers should have to prove the synthetic drugs they were importing had a legitimate use.
He said existing laws meant law enforcement had to test the drugs to prove they were illegal when that burden should rest with retailers.
Late last month the State Government listed an extra 33 substances to the Poisons Act in an effort to make it easier to police illicit psychoactive substances.