An appellate court ruled Thursday that Arizona colleges and universities can prohibit medical marijuana on campuses but lawmakers can't make it a crime.

The medical-marijuana law approved by Arizona voters in 2010 allowed cardholders to possess small amounts of marijuana but it prohibited possession in prisons, schools and on school buses.

The ruling Thursday struck down a 2012 decision by the Legislature to expand the off-limits list by adding college and university campuses.

However, the Court of Appeals ruling said colleges and universities can still forbid possession of medical pot under their own rules.

It said the 2012 move by the state to forbid pot on campuses violated the Arizona Constitution's protections for voter-approved laws.

Expanding the list of places where medical marijuana is prohibited doesn't "further the purpose" of the voter-approved medical-marijuana law and even "eliminates some of its protections," Judge Peter Swann wrote in the ruling.

MORE: Arizona marijuana laws: 13 things you need to know 

Conviction overturned by ruling

The decision overturned a medical-marijuana cardholder's 2015 conviction for possession of a small quantity of pot in his Arizona State University dorm room.

ASU police found the man's pot card in his wallet and got a warrant to search his room after the man was arrested while sitting on a campus street. Authorities say the man told an officer he had pot in his room.

Spokesman Ryan Anderson said the Arizona Attorney General's Office was disappointed by the ruling Thursday but hadn't decided whether to appeal it to the state Supreme Court.

The state had argued that permitting marijuana use on campuses would jeopardize federal funding for colleges and universities.

However, the ruling said the state and other landowners still can regulate what items or materials are taken onto their property, so a person violating an educational institution's restrictions could be removed from the property or charged with trespassing.

"If the state finds it necessary to protect federal funding by prohibiting medical marijuana on public college and university campuses, then the (medical-marijuana law) does not stop it from creating such policies," Swann wrote. "Nor does (the law) prohibit the Legislature from enacting non-criminal statutes to ensure the absence of medical marijuana on college and university campuses."

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