Organizers want to make this year’s Denver 4/20 marijuana rally into a larger-than-ever festival celebrating the first legal pot sales anywhere in the world.

But Denver city officials are weighing whether they will issue a permit to use Civic Center, leaving the two-day April event in question this year.

A turning point of sorts came last week, when an attorney for the event sent an eyebrow-raising letter to city officials putting them on notice that organizers would encourage attendees to toke in the park.

The letter asks for the city’s permission for adults to consume marijuana, although attorney and activist Robert Corry also asserts that the city’s OK isn’t needed.

“We would welcome Denver’s recognition of reality,” Corry wrote, saying that the organizers, as permit-holders, could control cannabis rules during the festival.

Amendment 64, passed by Colorado voters in 2012, allows the private sale and use of recreational marijuana.

But the constitutional law still bans public consumption of pot.

Scott Martinez, Denver’s city attorney, says last week’s letter and the knowledge that organizers will encourage pot use by 4/20 attendees will factor into the permit decision.

“We’ve received it, and we’re analyzing and seeing whether it affects any of our duties as a city,” Martinez said Wednesday.

That a cloud of marijuana smoke might drift above Civic Center during the April 19-20 event — particularly at 4:20 p.m. on April 20, a holiday for pot enthusiasts — is hardly a surprise.

For years, Denver police have treaded lightly, avoiding aggressive arrests or citations during an event that draws tens of thousands. That was true last year, when an outbreak of gunfire during the haze-filled rally injured three people and sent attendees running for cover.

But organizers have left it up to attendees whether to smoke pot.

City Councilman Charlie Brown said Corry and organizer Miguel Lopez were brazen to send the letter. He urged the city to reward them with a permit denial.

“It’s a lot of hootin’ and hollerin’, and I don’t think it’s worthy of the term attorney at the top,” Brown said. “They’re acting like claim jumpers, like they’re going to take the park back from the people.”

He also said the event’s occurrence on Easter Sunday this year, within blocks of several churches, would be unfortunate.

Corry has run into trouble over public smoking of marijuana, including at a September Colorado Rockies game, and is one of the most vocal local marijuana legalization advocates.

He said Brown’s recent suggestions of a police crackdown at the 4/20 event have worried potential attendees, even if Denver police haven’t announced any change in approach.

“That’s why we sent a letter: to send a notice to City Council that this is our interpretation of the law, … just so there’s no confusion,” Corry told The Denver Post.

Corry’s legal analysis essentially says smoking pot in Civic Center park should be allowed as long as organizers obtain a permit to use the area.

He cited a section of Amendment 64 that says anyone or any entity that “occupies, owns or controls a property” may regulate possession, use, distribution or sale of cannabis.

“On 4/20, Denver’s Civic Center Park is Our ‘Castle,’ ” Corry wrote in the five-page letter, addressed to Mayor Michael Hancock, Martinez and City Council. “My clients and I respectfully advise the City and County of Denver that we will be” allowing consumption and distribution by adults 21 and older.

An expert on marijuana legalization questioned Corry’s interpretation.

“What Amendment 64 made clear is that use in public where (marijuana) could be seen by other people was prohibited,” said Sam Kamin, a University of Denver law professor. “What (Corry) is suggesting, while it’s a novel theory, probably is not going to go very far.”

Corry’s letter notes several events a year in Civic Center that offer legal alcohol sales and consumption.

The issue has presented a challenge for city officials. While Brown has backed a crackdown, Councilman Chris Nevitt suggested a one-day public pot amnesty on April 20. Others shot down the idea.

And perceptions about the event have made some advocates uncomfortable.

“The industry has spent a great deal of time creating partnerships with the city and other groups,” said Mike Elliott, the executive director of the Marijuana Industry Group. “And while the 4/20 rally is not really within the scope of our group, we hope the city and the organizers do everything possible to ensure that people under the age of 21 aren’t there consuming marijuana.”

He declined to take a side in the permit dispute.

City officials probably will decide the issue in coming weeks.

“My guess,” Kamin said, “is that they will reject (Corry’s) interpretation, and it’ll end up in court.”

Corry says a lawsuit over public pot-smoking rules is not his intent.

But Brown said a fight might be unavoidable.

“If we’re going to take it to court at some point,” he said, “we might as well do it this year.”

Jon Murray: 303-954-1405, jmurray@denverpost.com or twitter.com/denverJonMurray.