What to Know Outside the home, adults 21 or over can possess up to 1 ounce of marijuana. Inside the home, adults 21 or over may possess up to 10 ounces.

Recreational marijuana cannot be sold in any form in Massachusetts without a retail license.

Using pot is illegal in any public place. You can't, for example, walk down the street smoking a joint the way you would a cigarette.

Recreational marijuana is legal in Massachusetts. Legal, but not readily available.

The ballot question approved by voters Nov. 8 went into effect Thursday, allowing adults to have limited quantities of marijuana for recreational purposes and grow pot plants in their homes. The catch: It's still illegal to sell marijuana in Massachusetts — except to registered medical marijuana patients — and will remain so for at least a year until the first pot shops are licensed and regulated.

For now, it's smoke 'em if you got 'em.

"For the average citizen ... this is going to mean they have to wait a while until they can go into a store or facility and purchase marijuana over the counter," said Martin W. Healy, chief legal counsel for the Massachusetts Bar Association.

Healy and other legal analysts say the lag-time and other provisions in the new law could initially cause confusion for marijuana users and possibly law enforcement, as well.

Recreational pot supporters agree. Jim Borghesani, spokesman for the group RegulateMass, which sponsored the ballot initiative, sees the first year or so as a "gray period" of sorts.

"It is legal to possess," said Borghesani. "It is illegal to sell without a retail license and retail licenses won't be available for quite a while."

States that previously legalized marijuana went through similar transition periods without major problems, he added.

In Colorado, where voters legalized recreational pot in late 2012, marijuana arrests dropped significantly in the 13 months or so it took for the state to regulate the drug and allow the opening of stores.

Voters in California, Nevada and Maine also backed legalization in the most recent election and like Massachusetts, all will experience gaps between the time pot becomes legal to possess and when it can be legally sold to consumers.

Before and after retail sales begin, the list of things you can't do with pot remains a lengthy one.

Norwood Police Chief William Brooks III, who serves as president of the Massachusetts Chiefs of Police Association, noted that possession of small amounts of marijuana outside the home has been decriminalized for the past eight years in the state, so in that respect the new law "is not a big change," he said.

But the home grow provisions could pose challenges for officers responding to a call at a person's home, Brooks said, as they may need to determine whether the amount of pot being cultivated is within proper limits. He also worries about a potential uptick in motorists driving while under the influence of marijuana.

A closer look at what can and can't be done once the law takes effect:

WHAT IS LEGAL?

- Outside the home, adults 21 or over can possess up to 1 ounce of marijuana.

- Inside the home, adults 21 or over may possess up to 10 ounces of pot. A single individual may cultivate up to 6 marijuana plants for personal use, and up to 12 plants per household are allowed if more than one adult lives on the premises.

- It's OK for one adult to give away up to an ounce of pot to another adult, but not for money.

WHAT ISN'T LEGAL?

- Recreational marijuana cannot be sold in any form in Massachusetts without a retail license. A Cannabis Control Commission, yet to be named, will be responsible for issuing retail licenses.

- Marijuana cannot be possessed, purchased, grown or used by anyone under age 21 (unless they have a valid medical marijuana permit), and it's against the law to give away pot to someone under 21.

- Using pot is illegal in any public place. You can't, for example, walk down the street smoking a joint the way you would a cigarette. It's also illegal to use pot in any place where tobacco is banned.

- Possession of any amount of marijuana remains illegal on school grounds.

- Laws against operating cars and other vehicles under the influence of marijuana are unchanged.

- Open containers or partially consumed packages of marijuana cannot be kept in a motor vehicle, except in the trunk or a locked glove compartment.

- Pot growing at home must be done discreetly and securely. Marijuana plants cannot be plainly visible from the street or any public area and must be cultivated someplace where there is a security device.

- Tenants cannot grow pot in their residences or smoke it if their landlord has a rule against it.

- Since marijuana is still barred under federal law, it can't be brought across state lines, sent by United States mail or used on federal property.