LYNN – Police Chief Kevin Coppinger challenged Classical High School students to mark Law Day Thursday by thinking about marijuana use against the backdrop of nationwide changes in how the drug is regulated.Without referring directly to the school or to the more than 1,000 students assembled in Classical’s auditorium, Coppinger spoke briefly about marijuana legalization efforts across the country.”I know a lot of people smoke weed. Some day I’ll come back and discuss the downside of that,” Coppinger said.Some students in the auditorium cheered and hooted when Coppinger mentioned marijuana, but student Haley Sheehan said the outbursts were not so much an endorsement of the drug’s use as attempts at injecting humor into the assembly’s serious topic.Coppinger received a standing ovation from the assembly at the end of his speech.Sheehan and four other students spoke during the hour-long assembly, and Sheehan reminded her audience, “Every decision you make is protected by the law,” adding, “obedience to the law brings more freedom.”During an interview following the assembly, she said marijuana’s status as a mostly illegal drug makes its use attractive to some students. She wonders how police will enforce safe driving practices if and when the drug is legalized.Law Day participant Rebecca Potter said legalizing marijuana does not eliminate problems associated with the drug’s use.”You’re still under the influence,” she said.Since 2008, possession of an ounce or less of marijuana has been decriminalized in Massachusetts with only a civil fine associated with possession. The state’s medical marijuana dispensing law took effect in 2013, and state health officials are currently reviewing dispensary applications.In an interview following his speech Thursday, Coppinger said police in states where marijuana has been legalized have been dealing with crimes associated with the drug, including thefts, explosions in homes where residents are growing marijuana plants, and transportation of the drug into states where marijuana is illegal.Coppinger said decriminalization in Massachusetts has reinforced the impression in young people that “there is nothing wrong” with marijuana use. He also said “there is great potential” for marijuana use leading to use of other drugs.But Sheehan, Potter and student Brian Maldonado disagreed among themselves about marijuana’s potential as a “gateway” drug.”I’m torn – what about kids growing up?” asked Potter.With seniors finishing school in under a month, Coppinger urged students to make smart decisions and be careful during summer months.”There’s always a tragedy, unfortunately: Use your heads – think about what you are doing,” he said.