By virtue of a single comma, the Colorado attorney general’s office says making marijuana hash oil at home is still illegal under state law, despite other laws legalizing marijuana use, cultivation and possession.

The opinion of the state’s top lawyer comes in a brief filed in a criminal case against a Mesa County man. The man, Eugene Christensen, is charged with arson, reckless endangerment and manufacture of marijuana concentrate. The last charge is a Class 3 drug felony, punishable by two to four years in prison.

Christensen has argued that the state’s law prohibiting manufacture of marijuana concentrate is now unconstitutional, after Colorado voters passed Amendment 64 in late 2012. The amendment legalizes limited possession of marijuana concentrate and also contains a provision allowing for “processing” of marijuana plants.

Hash oil is made by dissolving the active chemicals from dried marijuana plants then evaporating the sometimes-flammable solvent to form a thick, potent glop.

“The clear and unmistakable language of the Colorado Constitution,” Christensen’s attorney wrote in a motion seeking to throw out the charge, as quoted in the attorney general’s brief, “is that it is legal in Colorado to process marijuana and marijuana concentrate and that such actions shall not be criminal offenses.”

But, in its brief, the attorney general’s office argues that Amendment 64 specifically exempts hash oil from its protections. The argument relies heavily on the amendment’s terminology and punctuation.

For instance, the attorney general’s brief argues the protection for “processing” marijuana does not cover hash oil extractions done at home because, in part, the definition of marijuana excludes “oil.”

In defining the term “marijuana,” Amendment 64 includes the caveat that the term “does not include industrial hemp, nor does it include fiber produced from the stalks, oil, or cake made from the seeds of the plant …”

It’s the comma after “oil” in that sentence on which the attorney general’s office hangs much of its argument. In a five-sentence footnote, the attorney general’s office argues that the exclusion of “oil” stands separately from any reference to industrial hemp or marijuana seeds.

“Construing the general term of ‘marijuana concentrate’ to include ‘oil’ would make the provision excluding ‘oil’ meaningless,” the office argues in the main body of its brief.

Christian Sederberg, one of Amendment 64’s authors, says he understands the concern over residential extractions of hash oil — which have been linked to a rising number of home explosions in Colorado — and agreed they should be banned. But he said the attorney general’s argument goes beyond what Amendment 64’s authors ever intended and could be used to ban hash oil possession.

In a statement, Colorado Attorney General John Suthers said voters wanted Amendment 64 to promote only responsible marijuana use.

“To decriminalize dangerous and unreasonable behavior in which people are getting hurt and houses are blowing up defies the intent of the voters,” Suthers said.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/johningold