Just because a man previously convicted of methamphetamine-related crimes didn't know it was now illegal for him to buy over-the-counter allergy medicine given his criminal history doesn't mean his rights were violated, a divided North Carolina Supreme Court ruled Friday.

A majority of the seven justices reversed a lower appeals court decision overturning the conviction of Austin Lynn Miller for buying one box of capsules at a Walmart in Boone in early 2014, barely a month after an expanded purchase prohibition law took effect.

Miller was barred from buying anything beyond minuscule amounts of the medicine because it contained pseudoephedrine, which can be used to make meth, due to his 2012 convictions on possession of meth and keeping a car or house to sell controlled substances.

A jury convicted Miller for possessing the allergy medicine. He received a suspended sentence with probation.

State law already required the nonprescription medicine to be kept behind the counter and mandated electronic record keeping to monitor whether a meth lab was buying up the drugs. Often purchasers follow screen prompts saying they understand buying the medicines in large quantities or too frequently is illegal.

Miller's lawyer argued his client's due process rights were violated because he had no knowledge the purchasing law had changed in December 2013 and that he didn't intend to violate the law. There were no signs in pharmacies about the changes, either, the attorney said.

A three-judge panel of the Court of Appeals ruled unanimously in March 2016 the law was unconstitutional as it applied to a convicted felon like Miller who failed to receive notice from the state that their "otherwise lawful conduct is criminalized" unless there's other proof the person knew about the law.

State attorneys argued that Miller's ignorance of the law was no excuse and that it was his intentional action of purchasing the medicine that led to the crime.

Writing the majority opinion, Justice Sam Ervin IV sided with the state and rejected Miller's arguments that the retail purchase was an innocuous act that raised no alarms about whether he was breaking the law.