Even the smell of marijuana wafting from your backyard could be illegal if Denver City Council passes a new ordinance.

Denver officials, responding to fears that public pot consumption could become an ever-present problem in the Mile High City, will propose a set of new rules for open consumption and possession of marijuana.

The ordinance, being introduced at a committee meeting Monday in advance of the legalization of retail pot sales in January, would specifically ban marijuana from parks and the 16th Street Mall. It also would prohibit smoking on private property if it is visible to the public, such as on a front porch or in a car, or if the odor of pot could be detected from a neighboring property.

“Your activities should not pervade others’ peace and ability to enjoy,” said Denver Mayor Michael Hancock. “Marijuana is one of those elements that can be quite pervasive and invasive. I shouldn’t have to smell your activities from your backyard.”

If the ordinance is approved by council and signed by the mayor, it would take effect immediately. Offenders could face a fine of $999 and up to a year in jail.

Mark Silverstein, legal director for American Civil Liberties Union of Colorado, called the ordinance a “tremendous overreach, ill-advised, unnecessary and unconstitutional.”

He said the ordinance would prohibit consumption in the privacy of a person’s living room if the windows are open or if the person can be seen from the street.

“It will inevitably prompt police and community confrontations,” he said. “Amendment 64 said to regulate marijuana like alcohol. This is not. No one risks a year in jail for drinking a beer in their fenced backyard. And as for the banning mere possession anywhere on the 16th Street Mall, … I cannot believe Amendment 64 allows cities to make it a crime to carry a legal product in your pocket as you walk on a public sidewalk or public right of way.”

Denver is one of the few cities in the state taking the first steps toward the legal sale of marijuana to anyone older than 21, which was approved by Colorado voters as a part of Amendment 64 last year.

In November, the city will ask voters to approve a 3.5 percent sales tax on pot that could be raised to 15 percent. A statewide ballot question also is asking approval for a 15 percent excise and a 10 percent sales tax that could be raised to 15 percent.

Last month, Denver’s City Council approved a stringent set of new rules and regulations for the retail businesses.

But the city has been vexed in the past by mass marijuana celebrations, such as the annual mass smoke-in at the 4/20 event at Civic Center, and recent joint giveaways during a political event that resulted in public pot smoking, which is already against the law.

Council members and civic and business leaders worry that Denver will lose tourists and offend families and others if public consumption of marijuana is tolerated.

The ordinance doesn’t specifically address the 4/20 event. Hancock said the event will still be allowed, but the associated pot smoking in the park will not.

“The organizers are going to have to think long and hard about the kind of risk they and their patrons will be taking by deciding to puff up at the park,” Hancock said. “We are not going to tolerate it anymore. It’s done. … We want to make very clear, now and forever, and that is zero tolerance.”

Hancock said he was outraged last month when a group opposing the statewide pot tax gave away hundreds of joints at Civic Center. After receiving their joints, many people fired up and the police stood back. No citations were issued.

At the time, police worried mass enforcement of a petty offense would have resulted in a riot.

“The public trusted the industry that this would be done in a responsible manner, and I think that was an in-your-face response,” Hancock said. “We need to be clear to folks that we aren’t going to tolerate it anymore.”

Councilman Chris Nevitt, who worked on the ordinance with Hancock’s administration, said the proposal gives police guidance. But he said police action during events such as 4/20 doesn’t make sense.

“If you are smoking marijuana in a park, we will chase you off,” Nevitt said. “If thousands of people are making a statement one day a year, we have to think that through. That is in a different category than ordinary offenses.”

Jeremy P. Meyer: 303-954-1367, jpmeyer@ denverpost.com or twitter.com/jpmeyerdpost