A court clerk magistrate agreed Wednesday to file criminal charges against one of the state’s leading proponents for the legalization of marijuana, for selling a cannabis-based oil product he says was used for medicinal purposes.

The decision could test the legality of selling cannabis-based hemp products in a state that has approved the use of marijuana for medicinal purposes, and where voters could decide in the fall on whether to legalize marijuana for recreational use.

A lawyer for marijuana advocate Bill Downing said Wednesday that his client has been targeted for his vocal support of legalizing marijuana.

“I’m bemused we’re going forward with anything,’’ said attorney John Swomley. “It’s like we’re taking one step forward, but two steps back.’’

Downing, 57, of Reading, faces nine counts based on his sale of the oil to undercover detectives who visited his Allston store, CBD Please. Some of the counts are for possession with intent to distribute a Class D drug, marijuana, and the rest are for possession with intent to distribute a Class C drug, THC. State chemists who tested the oil that was sold differed on how to classify the product.

Downing is scheduled to be arraigned on the charges on March 3.

Stephen Borelli, the clerk magistrate in the case, held a hearing in January on the request by Boston police to file criminal charges — a request Borelli granted Wednesday.

Legal analysts said that local police may ask a clerk magistrate to approve the filing of criminal charges in cases with no immediate danger to the public and no need for the defendant to be arrested. Borelli was only required to determine whether there was probable cause to pursue charges, not the merits of the case.

That determination will be made by a judge or jury and will require higher standards of proof, said Robert Sheketoff, a well-known criminal defense attorney in Massachusetts.

Swomley had argued during the January hearing that the CBD oil products do not contain enough THC — the psychoactive ingredient in marijuana — to be classified as an illegal drug.

Downing also testified during the hearing that the product is sold in other states, and because it has not been criminalized by the federal government, he thought it was legal in Massachusetts. “I [believed] it then, and I still do now,’’ he said.

Downing is a member of Bay State Repeal, and has long advocated for patients to have better access to medical marijuana, citing its effective treatment of a range of illnesses. He has said he uses a cannabis-infused cream to treat his gout.

Downing formerly operated Reading-based Yankee Care Givers, which he has admitted delivered cannabis products to roughly 1,000 patients. State officials forced him to shut down that business in 2014 because he was allowed to serve only as a “caregiver’’ to only one patient under regulations that were enacted when medical marijuana laws were first approved in 2012.

He then opened CBD Please in Allston in 2014, selling non-psychoactive cannabis products — such as sprays, salves, capsules, and hair care items derived from hemp oil — that were, in his view, intended for medical reasons and legal.

Beginning in 2014, authorities conducted an undercover operation in which detectives went into Downing’s store and bought cannabis-laced oil that he told them could help with sleep or with back pain. The criminal charges are based on those sales.

Authorities also seized hundreds of grams of other oils and products that were at the store, but no charges were filed related to those products.

According to court records, the investigation was based, in part, on Downing’s own statements in published news reports and in a press release issued by the Massachusetts Cannabis Reform Coalition, announcing the opening of the store.

Milton J. Valencia can be reached at MValencia@ globe.com.