The legal age to buy cigarettes, e-cigarettes and other tobacco products will be 21 in Massachusetts beginning in 2019.
"Raising the age to buy tobacco products in the Commonwealth is an important step to prevent addiction for young people and encourage healthy choices," said Baker in signing the Tobacco 21 legislation in July.
About half of the state's cities and towns, including Boston, had already bumped the legal age up from 18 to 21, but the new law makes it a statewide standard.
The law exempts anyone who turned 18 by Dec. 31 and could already legally purchase tobacco.
"If you don’t have an ID, we're not going to serve you," said Geoffrey Yalenezian, who owns the Brennan's Smoke Shop chain. "As of today, all Brennan’s Smoke Shops are 21 plus."
The law imposes penalties on retailers who sell tobacco to underage customers but does not make it a crime for minors to smoke.
Before Monday, the legal age to purchase tobacco wasn't the same in every city and town. Nearly 200 communities in Massachusetts raised the age to 21 before the state law took effect, and Yalenezian said that sometimes caused confusion.
"I go to a different store every hour or two," said Yalenezian. "If I'm behind the counter, I have to help somebody. I'm like, 'Wait! What town — what town are we in? What's the age?'"
Smoker Mark Masters says he supports the new law because he regrets ever starting the habit.
"It's a dirty habit, a nasty habit, and an expensive habit," he said.
But Dave Mendes, who NBC10 Boston found picking up a couple of packs of cigarettes for his wife, said he doesn't think the new law will change anything.
"The kids are going to find a way to do it anyway. It's just the way it is," Mendes said.