Some providers testified they would be forced to close if they couldn't charge for their product and could only provide it to three cardholders.
Reynolds noted in the decision that Montana had 8,404 registered cardholders in November. Of that number, 5,211 rely on providers to supply them with medical marijuana, and there are 293 registered providers. The rest grow their own.
Even if all 293 current providers stayed in business under the new limitations, they would only be able to provide marijuana to a maximum of 879 cardholders by law, Reynolds wrote.
"This means that approximately 4,332 of the currently registered cardholders would have no source of medical marijuana. These are presumably the cardholders with the most severe medical conditions preventing them from growing their own medical marijuana," he said.
Reynolds concluded the cardholders would be injured or irreparably harmed if the ban on commercial transactions went into effect.
"The court can envision few forms of injury or harm more substantial than to deprive persons with debilitating medical conditions of what may be the only form of effective relief from those conditions as testified to before the court," he wrote.
Montanans voted to keep the 2011 law in a November referendum.