Anthony Orozco, 19, a community college student and soccer player in southeastern Colorado, is facing criminal charges for something that will soon be legal across this state: the possession of a few nuggets of marijuana and a pipe he used to smoke it.

Mr. Orozco said that one day in September he and a few friends were driving in Lamar, on the plains near the Kansas border, when they were pulled over. After the police officer found marijuana in the car, Mr. Orozco was issued a summons for possession and drug paraphernalia — petty offenses that each carry a $100 fine — and given a court date.

“We get treated like criminals,” Mr. Orozco said.