South Koreans who use cannabis while in Canada or US could face criminal charges when they return to their home country, Korean police are warning.

An official from South Korea’s narcotics unit gave the message earlier this week, saying marijuana is treated as a serious offence. Violators could face up to five years in prison.

READ MORE: A visitor’s guide to smoking legal marijuana in Canada Or US

“Weed smokers will be punished according to the Korean law, even if they did so in countries where smoking marijuana is legal. There won’t be an exception,” said the official, according to the Korea Times.

The South Korea government also put out a warning last week, the day before Canada legalized marijuana.

On Oct. 16, the South Korean Embassy in Canada said on Twitter: “Even if South Koreans are in a region where marijuana is legal, it will be illegal for them to consume it. Please take care not to commit an illegal act and be punished.”