MCALESTER, Okla. (AP) — A medical marijuana advocate from Colorado is facing a felony drug charge after a traffic stop in Oklahoma that her attorney called unconstitutional.

Regina Nelson, 54 of Boulder faces one count of marijuana possession with intent to distribute, according to the McAlester News-Capital. The Oklahoma Highway Patrol arrested Nelson on Sunday near McAlester after a trooper reported finding marijuana and drug paraphernalia in the vehicle she was driving.

Nelson's 24-year-old son, Bryan Elliott Laufenbert, of Katy, Texas, and fellow advocate Michael Browning, of Boulder, also face the drug selling charge. All three were released on $5,000 bond and have pleaded not guilty.

Court documents said Trooper Ashby Sutherland stopped the vehicle for failing to use a turn signal. Sutherland searched the vehicle and said he found four joints, 11 containers with what appeared to be cannabis leaves, oil capsules, hand cream, peanut butter and a digital scale.

Attorney Brecken Wagner of McAlester is representing Nelson and said he will file motions challenging the constitutionality of the "stop-and-search." Wagner said Nelson was targeted for a Colorado license plate.

"My client experienced what many people experience for having the audacity for driving with an out-of-state plate," Wagner said. "They tend to get pulled over and searched and harassed."

Nelson had scheduled speaking engagements in Oklahoma, where voters can consider legalizing medical marijuana on a June 26 ballot. Nelson has authored books on the medical use of cannabis.

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Information from: McAlester News-Capital, http://www.mcalesternews.com