The possession of an ounce or less of marijuana will be decriminalized, dog racing will banned by 2010, and the state income tax isn’t going away, Massachusetts residents decided on Tuesday when they voted on three state-wide ballot questions.

When the law governing marijuana goes into effect in November or December, people will not be arrested for the possession of small quantities of marijuana, said Whitney Taylor, the chairwoman of the Committee for Sensible Marijuana Policy, an advocacy group that supports decriminalization.

The effect, Taylor said, will be that people “won’t be punished for the rest of their lives” if they are caught with the drug. Instead, people over 18 will face a fine of $100, and minors will have to complete a drug awareness program and perform community service.

Whitney said that while the “legislature can always introduce a new vote” to overturn the initiative, she said that the 65 percent of the vote that the initiative received constitutes “a mandate.”

“Politicians wish they won their races by 65 percent of the vote,” she said.

Students and professors interviewed were supportive of the initiative.

“It’s a small step, because it doesn’t change the laws radically,” said Jeffrey A. Miron, a Harvard economics professor.

But the implications for Harvard students are “very, very small,” he said, because marijuana will still be illegal. And the change in the law will not alter Harvard’s policies on illegal drug possession.

“Harvard is still perfectly free to set whatever policy it wants,” Miron said.

Charles R. Nesson ’60, a professor at Harvard Law School who filed a lawsuit earlier this year challenging the constitutionality of drug laws, said he was “very pleased” with the passage of the initiative.

Nesson said it was a “very big step conceptually,” because “it recognizes that doing something that harms no one is not an appropriate basis for making someone a criminal.” But as far as actually changing anything, Nesson added, it was a “very small step.”

Intiya Isaza-Figueroa ’10, a native of North Hampton, Mass., said she voted to decriminalize marijuana, but that she does not believe that the initiative will reduce social stigmas about marijuana use.

Diana G. Kimball ’09, a native of Ann Arbor, Mich. who is registered in Cambridge, said she voted to decriminalize marijuana because “having a criminal record is really serious,” but added that she generally feels less educated about the ballot questions than about the presidential race.

“I made the decision that rang liberal to me,” she said when deciding which initiatives to vote for.

The same philosophy guided her on the other two initiatives as well: when it came to deciding whether to ban dog racing, Kimball said, “Cruelty is usually a pretty good thing to get rid of.”

But the ban on dog racing proved to be the most controversial of the three—it passed 56 to 44, the smallest margin of the initiatives.

Isaza-Figueroa said she voted against it.

“I don’t bet on dog racing personally,” she said. “I don’t think it was a significant part of our industry.”

The ballot question on the income tax was decided by the largest margin, with 70 percent voting to keep the income tax and 30 percent voting to abolish it.

Thuy N. Quan ’11 said she voted against the question because Massachusetts is already “billions of dollars in debt.”

She questioned where funding for public schools would come from if the initiative had passed.