Medical marijuana is dispensed Friday at the Takoma Wellness Center in Washington. A ballot initiative next month will let city residents decide whether to legalize marijuana. (Evelyn Hockstein/For The Washington Post)

D.C. voters are likely to legalize marijuana possession in the District next month. But it could be many more months, perhaps a year or more, before residents would be able to legally purchase non-medicinal marijuana.

And in the interim, the organizers of the ballot initiative — which is supported by nearly two-thirds of likely voters, according to recent polls — are warning lawmakers not to delay its basic provisions of the voter initiative, which would allow the possession of up to two ounces of marijuana and the home cultivation of as many as six cannabis plants.

But D.C. Council members — who have the power to modify the initiative, delay it or overturn it entirely — appear determined to move forward carefully, in keeping with their previous efforts to implement a medical-marijuana initiative.

“I don’t want uncertainty to be out there in the streets and in the market, and the initiative as it is written doesn’t give us the certainty we need,” said David Grosso (I-At Large), who is perhaps the council’s most outspoken advocate of legalization. “It may be easier to just delay the whole thing while we come up with the regulatory framework.”

Grosso, who introduced a bill more than a year ago establishing a possible framework for the regulation and taxation of marijuana sales, said if the initiative passes, the council should step in and delay its effect until a regulatory regime can be rolled out.

View Graphic The status of marijuana laws across the nation.

That, he said, could be late summer, or even as late as October 2015, when the District’s new fiscal year begins.

The coalition of activists who are promoting the ballot measure, known as Initiative 71, is pushing back at any suggestion of delay, however. The activists concede that developing a system of regulation and taxation may take time to develop but say that that shouldn’t forestall the legalization of possession and home cultivation.

Malik Burnett, a medical doctor who is helping organize support for the initiative, said he has had generally positive conversations with lawmakers, who have tended to support the sentiment behind it but are concerned about how best to regulate sales and protect the public from potential wrongdoing.

“I can understand their mind-set on that,” he said of the council. “But I don’t think they should in any way interfere in the will of the voters.”

Two D.C. Council committees have scheduled a hearing for Oct. 30 to start exploring how to manage the post-initiative landscape. Vincent B. Orange (D-At Large), the chairman of one of the committees, said he has started researching aspects of the legalization measures in Colorado and Washington state.

Among his concerns: the rate of taxation, and how the public funds generated by marijuana sales will be used in those states. “It could be an opportunity to generate a tremendous amount of tax revenue,” he said. “But from my point of view, it has to be set up right.”

Grosso’s bill, as introduced, would levy a 15 percent tax on the gross sales of non-medical marijuana and 6 percent on medical marijuana. Those funds, as well as fees charged to cultivators and retailers, would be earmarked to a variety of agencies and programs, including police training, youth programs and efforts to combat substance abuse.

View Graphic Support for legalized marijuana in D.C.

Orange suggested that education and affordable-housing efforts might also benefit from marijuana revenue, which has not yet been officially estimated by city financial officials. “If we’re going to go in this direction, we should look at some of our pressing needs right now,” he said.

The responsibility for regulating marijuana, under Grosso’s bill, would rest with the District’s alcohol regulators. The District’s existing medical marijuana program is regulated through the city health department, and council members have speculated that those rules could form the basis for a broader system of marijuana sales.

Otherwise, the biggest outstanding question appears to be what happens in the period between when the initiative becomes law and when the council is able to pass a bill establishing a regulatory regime.

Advocates are pressing the council to leave their hands off, allowing the possession and cultivation measures.

“This won’t happen overnight, and it didn’t happen overnight in Colorado,” said Adam Eidinger, another activist for Initiative 71. “But what did happen is that they stopped arresting people, they let people grow their own and keep what they grew. There was no regulation in place other than that.”

Eidinger said he expects “some sanding of the rough edges” from the council if the initiative passes. But delaying the initiative’s effect while a regulatory bill is drafted, he said, would create confusion and increase the likelihood of congressional intervention.

Much depends on whether Congress steps in to block the initiative or otherwise interfere. But attempts by congressional Republicans to overturn the city’s marijuana decriminalization law have been unsuccessful, and the advocates and council members are proceeding under the assumption that the bill will not be challenged.

Should the initiative succeed, it would be transmitted to Congress for a 30-legislative-day review period probably late next month or in early December, meaning its provisions could take effect as soon as late January. And even if the council moves to delay its effect, the vagaries of national politics have local leaders mindful that there is no reason to dawdle.

“We have to move on this while President Obama is in office,” Grosso said. “I don’t know what happens after that.”