On the day marijuana legalization took effect, one of the chief opponents of the new law expressed skepticism about raising the legal age of consumption and said he would not pursue a moratorium in Boston.

“The people of Boston overwhelmingly supported the law, and I’m going to follow the will of the voters,” Boston Mayor Marty Walsh told reporters on a visit to the State House on Thursday. He said, “There’s probably a small fraction of people that would like a moratorium, but it’s the law, so we’re going to live under the rules of the law.”

The ballot law passed by voters in November legalized possession, gifting and growing the green drug on Thursday for those 21 and older, while setting out a timeline for the regulation of retail marijuana stores. Unregulated sales remain illegal.

Under the law cities and towns can bar any marijuana establishments from their municipality only by a local referendum.

Walsh said he hopes to work with the Legislature, where leaders have expressed interest in making changes to the new law, with some attention to zoning.

“Boston is the biggest city in the Commonwealth, and probably will be one of the most affected cities in the Commonwealth, so want to see exactly what the regulations will be,” Walsh said. He said, “There is some concern about zoning.”

More than a month after the question’s passage, Senate President Stan Rosenberg, who voted in favor of it, said this week that lawmakers should consider raising the marijuana age from 21 to 25.

“I think that’s difficult,” Walsh said. He said, “I think that would be complicated to do especially when the drinking age is 21.”

To celebrate legalization, a small group of activists gathered outside the State House where they gave one another marijuana gifts.

Asked about that, Walsh said there were many “warning signs” that he and others raised trying to discourage voters from passing the ballot measure.

“It’s the law. It’s the way it was written,” said Walsh, who said he is concerned about public safety, including the difficulty police face in determining whether someone was driving while intoxicated by marijuana.

According to an official in the Treasury, which oversees the Alcoholic Beverages Control Commission, licenses are required for the distribution of alcohol, but people can give a bottle to a friend.

Gov. Charlie Baker, who returned from Israel on Thursday, also responded to the State House gathering: “It’s legal. I just hope everybody pays attention to the rules.”

Baker said it is important that lawmakers respect the will of the voters, but indicated he would be open to delaying the implementation of some aspects of the law if it meant strengthening public safety and health protections.

“As long as the delay is what I would describe as a reasonable time period I think we would support that,” Baker said.

Walsh was at the State House on Thursday when departing members of the House - where Walsh once served - said their goodbyes to the chamber.