Marijuana tourism is on the way to Colorado, under a recommendation made Tuesday by a state task force to regulate the drug made legal by voters last year.

But Colorado should erect signs in airports and borders telling visitors they can't take pot home, the task force recommended.

Colorado's marijuana task force was assembled to suggest regulations for pot after voters chose to flout federal drug law and allow its use without a doctor's recommendation. Made up of lawmakers, law enforcement authorities and marijuana activists, the task force agreed Tuesday that the constitutional amendment on marijuana simply says that adults over 21 can use the drug, not just Colorado residents. If lawmakers agree with the recommendation, tourists would be free to buy and smoke marijuana.

"Imposing a residency requirement would almost certainly create a black market for recreational marijuana in the state," said Rep. Dan Pabon, a Denver Democrat who sits on the task force.

Tourists could see purchasing caps though, possibly as low as an eighth of an ounce per transaction.

Afraid that marijuana tourism could open the door for traffickers to load up and take it across state borders for illegal sale, task force members agreed that non-residents should be able to buy only limited amounts, though a specific amount wasn't set.

"Marijuana purchased in Colorado must stay in Colorado," Pabon warned.

"We could attract greater federal scrutiny and displeasure of our neighbors," if marijuana flows across state lines, he said.

Task force members were less successful agreeing to recommendations on marijuana growing and public use. Colorado's marijuana law allows home growing but requires plants to be in a locked, secure location out of public view. The task force couldn't agree whether a "locked" and "secure" location would mean a backyard surrounded by a fence, or whether an enclosure such as a shed or greenhouse should be mandatory.

One of the task force's most vocal marijuana critics, Greenwood Village Police Chief John Jackson, worried that backyard pot gardens would need more than a chain-link fence to keep kids out.

Not all task force members agreed. User advocate Meg Sanders said the covering requirement wouldn't be fair to rural Coloradans.

"I think it goes too far in restricting what people can do on their own private property," Sanders said.

Public use also prompted a dispute that wasn't resolved Tuesday. Jackson and others wanted to ban marijuana use on publicly visible patios, porches and backyard. Marijuana activists chafed.

"So I can drink a beer on my porch? But I can't smoke a joint?" asked marijuana advocate Christian Sederberg.

State Sen. Cheri Jahn, D-Wheat Ridge, said lawmakers would hesitate to regulate something legal people do on private property. What about backyard grills that send the smell of hamburgers into the nose of a neighbor who's vegetarian?, she asked.

"I don't know how far we want to go telling people what they can't do on their own porches," she said.

The porch marijuana question was left unsettled. Task force members also put off a decision on proposals from Jackson to exempt law enforcement from maintaining marijuana and marijuana plants seized during criminal investigations.

Potency and labeling recommendations for commercial marijuana will also be discussed later.

The task force has until Feb. 28 to recommend marijuana regulations, which will ultimately be set by the state Legislature and the Department of Revenue, the agency which oversees gambling and alcohol and will also regulate recreational pot.