A Minnesota-based medical marijuana company says Google is blocking its attempts to advertise online.

Vireo, the parent company of Minnesota Medical Solutions, tried to take out a series of online ads in New York, where it operates four clinics and is one of several companies chosen by that state to grow and manufacture medical cannabis. Each time, Google rejected the ads, citing its policy against promoting “dangerous products or services.”

On Monday, the company expanded its online advertising efforts to include the two Minnesota clinics operated by Minnesota Medical Solutions. Enrollment in Minnesota’s medical cannabis program remains relatively low — 1,133 patients since legalization last July. But Vireo announced that it would also attempt to place “Minnesota-targeted Google ads to make it easier for Minnesota patients to learn about using our medicines.”

Google did not respond to calls and e-mail inquiries Tuesday, but the company draws a line between acceptable and unacceptable online advertisements: “We want to help keep people safe both online and offline, so we don’t allow the promotion of some products or services that cause damage, harm, or injury,” the guidelines begin. The list of products Google will not advertise runs from explosives to tobacco to “recreational drugs and drug-related equipment.”

Dr. Kyle Kingsley, founder and CEO of MinnMed and Vireo, argues that medical marijuana is a pharmaceutical, and should be advertised online just like other treatments for epilepsy, cancer or glaucoma. Almost half of all states have legalized cannabis for medical use, but the federal government still classifies it as an illegal, dangerous drug with no recognized medical value, and Google’s ad policies appear to follow suit.

“As a physician, it’s hard to understand why Google willingly accepts ads that promote highly addictive painkillers, like OxyContin, that are responsible for thousands of deaths each year, but knowingly rejects medical cannabis ads that could, in many cases, be a significantly safer therapeutic option for patients,” Kingsley said in a statement.

He added: “I think it is going to be challenging for Google to explain why it is comfortable accepting advertisements from companies that promote the sale of alcohol, knives, hatchets and infidelity, but is uncomfortable accepting ads from medical cannabis companies. We don’t live in a black-and-white world, and Google ought to adopt more thoughtful and nuanced advertising policies.”

While 23 states have legalized medical marijuana, and four states have legalized its recreational use, the federal ban has made it difficult for cannabis companies to operate like regular businesses. Banks and credit card companies are reluctant to do business with companies that sell a banned federal substance. Cannabis companies also miss out on tax breaks and face constant scrutiny from state and federal law enforcement.

Minnesota’s medical cannabis program is one of the most tightly regulated in the nation. The state strictly limits who can use medical marijuana, who can sell it, and in what form.

Only two companies — MinnMed and LeafLine Labs — can grow, refine and sell cannabis. The product can only be sold in pills and liquids. Smoking the raw plant form remains illegal.

Currently, the state has just three clinics, although the number will expand to eight by this summer. Only patients with one of a limited number of serious illnesses can register with the state to buy medical cannabis, although the program will expand in August to include patients suffering from intractable pain — a move that could potentially bring in thousands of new customers.

As of Tuesday afternoon, Google had not responded to MinnMed’s request.