Should 20-year-olds be allowed to smoke? Why Hawaii says no.

On January 1, Hawaii became the first state to raise the legal smoking age to 21, taking a strong stance that medical researchers say could save thousands of lives.

In most of the United States, the minimum age to buy tobacco is 18, part of the campaign against smoking that was set in motion by the surgeon general's 1964 report on its health hazards. For years before that, some doctors had touted tobacco as a healthy habit, with companies adopting slogans like "For digestion's sake ... Smoke Camels!" and "More doctors smoke Camels."

Since then, awareness campaigns and mandatory warnings on tobacco packaging have helped save an estimated 8 million lives. Today, just 18 percent of Americans smoke, down from 43 percent in 1964.

"To go to the next level, we have to put an emphasis on this idea of creating a smoke-free generation," then-Acting Surgeon General Boris Lushniak told The Christian Science Monitor in January 2014. 

An overwhelming 90 percent of America's daily smokers began before age 19, according to the Institute of Medicine of the National Academies. And many teens start well before they turn 18, relying on their older peers to buy cigarettes for them. Increasing the minimum age for purchase by just three years, eliminates that option for many young teens. Medical research suggests that the age increase could reduce smoking by 12 percent by the time today's teenagers grow up.

"In Hawaii, about one in four students in high school try their first cigarette each year, and one in three who get hooked will die prematurely," Lola Irvin, an administrator at the Hawaii Department of Health, told the Associated Press. Hawaiian high-schoolers' e-cigarette use has quadrupled in the past four years.

About 75 percent of Americans say they support that age minimum, according to a poll from the Centers for Disease Control and Prevention, including 7 in 10 smokers. But the federal government's hands are tied: currently, the Food and Drug Administration is prohibited by the 2009 Family Smoking Prevention and Tobacco Control Act from setting a minimum above age 18. 

More than 100 communities have experimented with raising the minimum, beginning with Needham, Mass., in 2005. After ten years, the town's age-21 rule is credited with cutting teen smoking rates in half. Others communities have followed suit, from New York to nearby Boston, where a similar law will go into effect February 15. 

So far Hawaii is the only US state to adopt a minimum purchase age of 21, but California, Massachusetts, and Washington state have debated similar proposals. In Alabama, Alaska, New Jersey, and Utah, the minimum age is 19. 

Not everyone supports the ban, particularly on Hawaii's military bases. Leadership were enthusiastic about keeping soldiers healthier, but some servicemen told the Associated Press they found the new rule frustrating.

"If you can serve the country, you should be able to have a drink and a cigarette," said Justin Warren, 22, an Army X-ray technician.

As Hawaii implements the law, initial efforts will focus on education. First time offenders will be fined $10. After that, the fines go up to $50 and $2,000, respectively. Teens may perform community service instead of paying a penalty. Retailers that sell to underage smokers can expect a $500 fine. 

This report contains material from the Associated Press.