Melissa Etheridge was arrested for marijuana possession in August as she tried to cross the border from Canada into the United States.

According to documents obtained by celebrity news website TMZ, Etheridge’s tour bus was stopped by U.S. Customs and Border Patrol in North Dakota on Aug. 17 as she was returning to the country. The rocker and her band played in Parkland County, Alta., at the River Cree Resort & Casino the night before.

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Etheridge, 56, reportedly had marijuana oil on her bus, which was detected by border patrol canines. She was booked for possession of a controlled substance and had a mug shot taken. She pleaded not guilty. (Representatives for the singer have not replied to requests for comment.)

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Marijuana oil is illegal to possess and purchase in North Dakota. In Canada, if you possess a valid medical prescription, it’s legal to purchase from a licensed medical marijuana producer.

Etheridge has been an advocate for medicinal marijuana use for years now, ever since she survived breast cancer in 2005. She says cannabis helps manage pain from the illness.

Global News spoke with Etheridge in April, while she was in Toronto for the first-ever O’Cannabiz Conference & Expo. The gathering explored the latest marijuana regulations, industry standards and best practices for both medicinal and recreational marijuana in Canada. The singer was one of the keynote speakers.

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Etheridge says the plant has changed her life. In 2014, she teamed up with Greenway Dispensary in California to create a line of cannabis-infused wine, called Know Label Wine, and then in 2016, she launched her own company, Etheridge Farms, which produces legal cannabis products (in California only).

She hopes to expand her businesses north of the border, but it’s unclear if this incident will have any impact on her plans.

When Global News interviewed Etheridge, she referenced the incongruencies of travel across the border between the two neighbouring countries.

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“Do you know what’s weird?” she said in April. “I can have my legal cannabis [in California] and be in Canada and have my legal cannabis there, but I can’t fly from Canada to California with my cannabis. [Governments] really have to step up with how it’s changing and what’s happening. Once they take the fear out of it, then we can really move forward with it like you guys are. You’ll find there will be more jobs, the economy would be better, people are going to be healthier, there will be fewer opioid deaths, fewer alcohol deaths … really, the plus sides of this are astounding.”

Global News has reached out to U.S. Customs and Border Patrol for comment, but as of this writing has not received any reply.