TUCSON, Ariz. (CN) – Stubbing out a student’s conviction for pot possession, the Arizona Supreme Court found it unconstitutional Wednesday to prosecute registered users of medical marijuana for carrying the drug on college campuses.

The case stems from the March 2014 arrest of Andre Lee Juwaun Maestas while he was sitting in a road near his on-campus dormitory at Arizona State University.

While searching the student, an ASU police officer found a valid Arizona medical marijuana card in Maestas’ wallet. Acting on a search warrant then, the officer found 0.4 grams of weed in Maestas’ dorm room.

The amount is barely two-hundredths of the 2.5 ounces allowed under the Arizona Medical Marijuana Act, but Arizona has since 2012 made it illegal for even AMMA cardholders to possess marijuana on the campus of a public college.

In Maricopa County Superior Court, Maestas was convicted both of marijuana possession and obstructing a public road. He got probation and a fine on the marijuana charge.

In support of the prosecution, attorneys for the state argued that the continued federal classification of marijuana as a Schedule I drug, along with heroin and LSD, means that universities can penalize AMMA cardholders to protect their receipt of federal funding.

Schedule I is the highest level of classification under the Controlled Substances Act; the designation means that the drug has no accepted medical use and cannot legally be prescribed.

But Arizona’s argument failed to sway the state Supreme Court on Wednesday.

“Even if (state law) did authorize the legislature to take some action to preserve federal funding, criminalizing AMMA compliant marijuana possession or use is impermissible because it is unnecessary to achieve the statute’s purpose,” Justice John Pelander wrote in the 7-0 ruling. “The state has not shown that failing to ‘penalize a person solely for his status as a cardholder … would cause’ a school to lose federal funding.”

Pelander also noted that the AMMA specifically allows bans on school buses, at preschools, primary or secondary schools, or at correctional facilities. The law does not mention college campuses.

“Because the AMMA sets forth a list of locations where the legislature may impose ‘civil, criminal or other penalties’ when a person possesses or uses marijuana, and because that list does not include college and university campuses, we assume that the voters did not intend to criminalize AMMA-compliant possession or use of marijuana on public college and university campuses,” the 12-page ruling says.

The court further panned the state’s case by adding that the campus rules, which were passed by the Legislature, constitute an illegal amendment to the AMMA. Under Arizona state law, the Legislature can only amend a voter initiative with a three-fourths supermajority, which was not done in this case.

“The legislature amended the AMMA when it enacted (the campus ban) because that statute makes AMMA-compliant possession or use of marijuana on public college and university campuses criminal,” Pelander wrote.

In addition to vacating Maestas’ cannabis conviction, the court vacated a previous ruling in the case by the Court of Appeals.