Arizona’s medical marijuana patients can use, and dispensaries can sell, concentrated extracts made from marijuana, a Maricopa County Superior Court judge ruled Friday.

Many medical marijuana patients, doctors and dispensary owners have claimed that the concentrations made from the marijuana flowers are the safest and most effective way to treat acute medical conditions like seizures.

But Maricopa County Attorney Bill Montgomery said that, after reviewing older statutes and the 2010 voter-approved Arizona Medical Marijuana Act, he found different definitions for “marijuana” and “cannabis,” which led him to believe that one was legal for medical use and the other remained illegal for any use.

Montgomery told local police departments that, because of his office’s interpretation of the different definitions, marijuana extracts were still illegal and patients or dispensaries possessing or selling them could be arrested and prosecuted.

The American Civil Liberties Union led a lawsuit challenging Montgomery’s interpretation. To demonstrate a justiciable controversy, the ACLU highlighted a nine-year-old boy who suffers from seizures that are treated with marijuana extract.

The ruling is most immediately a victory for the parents of Zander Welton, a 5-year-old Mesa boy who has a doctor’s permission to use medical marijuana to treat his seizures.

Jacob and Jennifer Welton had been giving him a liquid tincture with marijuana extract until Maricopa County Attorney Bill Montgomery threatened to prosecute them and anyone who supplied the product. They said it was difficult to get the boy to swallow things like applesauce with crushed marijuana leaves, much less to determine he was getting the correct dosage.

But Judge Katherine Cooper’s ruling, unless overturned, sets the stage for the state’s 45,000 other medical marijuana patients to be able to obtain other products made not with the plant’s leaves but with extracts.

“It is undisputed that medical marijuana is intended to be used by patients to treat chronic, debilitation, and/or painful conditions,” the judge wrote, listing conditions in the 2010 law ranging from cancer and hepatitis to nausea, seizures and severe and chronic pain.

“It makes no sense to interpret the Arizona Medical Marijuana Act as allow people with these conditions to use medical marijuana but only if they take it in one particular form,” Cooper said. “Such an interpretation reduces, if not eliminates, medical marijuana as a treatment option for those who cannot take it in plant form, or could receive a greater benefit from an alternative form.”

Cooper explained in her ruling that voters chose to decriminalize the medical use of marijuana, which the citizen initiative defined as “the dried flowers of the marijuana plant, and any mixture or preparation thereof…”

Cooper said the plain language interpretation of that section, and in particular the part about “any mixture or preparation thereof” means extracts are covered by the state’s medical marijuana program.

She said extracts not only ensure proper doses but also can make it easier for patients who cannot consume the plant itself.

“The language of the Arizona Medical Marijuana Act and its ballot materials make clear the proponents and voters intended (the law) to provide access to medicine for debilitating medical conditions without fear of criminal prosecution,” Cooper said. And she said the statute “does not limit the form in which that medicine can be administered.”

Montgomery said Saturday he fears that once products start being made of extracts it will become more difficult, if not impossible, to restrict the program for strictly medical purposes.

He said there has been no decision whether to appeal. But he said Cooper may have to clarify whether the 2 1/2-ounce limit applies to the original plant material or what’s left after the extraction process.

At a hearing last month, Emma Andersson, an attorney with the American Civil Liberties Union, said using an extract — as opposed to grinding up the plant into Zander’s food — is more than a question of convenience.

“What Zander is not getting by using only plant material is an accurate dose of his medicine that is consistent every single time and the amount of cannabidiol he is supposed to be getting,” she told the judge. That refers to a non-psychoactive element of marijuana that Zander’s parents say helps control his seizures.

When Montgomery made his initial determination that extracts are illegal, that left the couple trying to feed Zander dried marijuana leaves, which they could still legally obtain, crushing it up into the child’s food. But his father told Capitol Media Services that’s not a real option.

“It’s a real fibrous material,” he said. “That’s kind of like taking hay and chopping it up into applesauce to him.”

And Zander, being a 5-year-old, figures out quickly what he doesn’t want.

“He starts to filter it through his teeth,” his father said.

His mother said other forms of administration, like smoking or even creating a tea, are unacceptable, at least in part because heating the plant releases the psychoactive properties of marijuana that would make the child “high.”

“That’s the part that we’re trying to stay away from,” she said.

Howard Fischer of Capitol Media Services contributed to this report.