A urine test taken in January showed that the MP was using three illegal drugs, among them morphine, that were not prescribed to him by his doctor.
Petzäll was kicked out of the Sweden Democrat party last summer, after he refused to give up his seat as an MP due to his addiction problems.
Earlier that year, Petzäll had taken a time-out from politics, after a drunken brawl when he was arrested by police. The party decided to support him through treatment.
But when he had a lapse a few months later, they demanded he's leave his seat in parliament. He refused, and after having finished his second treatment for addiction in september 2011, he told media he would continue in parliament as an independent, working with political issues related to addiction and substance abuse.