Guam has raised its smoking age from 18 to 21.
From Monday, it is illegal for individuals under 21 to smoke cigarettes or vape or access tobacco products, the Pacific Daily News reports.
Those caught smoking illegally will be required to go through a mandatory education program that includes smoking cessation, the law states.
Smoking rates in the island have declined in the past few years but remain higher than the national average, according to the American Cancer Society.
Health care professionals who supported the law cited a report by the Institute of Medicine which predicts tobacco use in the country would drop by 12 per cent if the legal smoking age was raised to 21.
The law had the support of young adults who signed petitions and spoke in favour of it, Speaker Benjamin Cruz said.
But some teens believe the change will lead to more people smoking illegally and have queried why they cannot smoke when they turn 18 if they can be charged for a crime as an adult at that age.
