LOS ANGELES, Calif. — Los Angeles voters will choose today between three options for regulating medical marijuana dispensaries and decide the fate of a symbolic resolution against unlimited campaign spending by corporations.

The three medical marijuana ballot measures are the culmination of years of debate over regulation and taxation of the operations. All three would prevent the shops from being shuttered, but they differ on the number that would be allowed to operate.

Of the three measures, only two are being actively backed by their respective campaigns. Ordinance E was abandoned by the group that collected petitions to get it on the ballot. Its supporters are instead backing Proposition D, a City Council-sponsored measure that would restrict the number of dispensaries to the 135 that registered before September 2007.

Proponents of Proposition D include medical marijuana advocates, council members and a labor union.

Ordinance F, meanwhile, would not set a limit on the number of dispensaries. It is also supported by a group of medical marijuana advocates.

The two campaigns both say their measures would allow marijuana dispensaries to open as long as they follow a set of criteria and regulations, including submitting to background checks and setting up shop a safe distance from places frequented by children.

There are some differences in the proposed regulations, with each campaign claiming to have better or stronger criteria.

According to proponents of Proposition D, their regulations adhere closer to existing state and federal requirements and have a better chance of being enforced, but Ordinance F proponents contend they have stronger restrictions, such as not allowing children into their dispensaries and requiring not just background checks, which both measures require, but also testing of volunteers and workers.

Ordinance F sets a 500-foot distance between shops and parks, child care facilities and other similarly “sensitive” sites, while Proposition D ups that distance to 600 feet. Both measures require a 1,000-foot buffer between medical marijuana businesses and schools.

Under Proposition D, the businesses would be allowed to operate between 10 a.m. and 8 p.m., while under Ordinance F, the stores could stay open until 10 p.m.

Ordinance F would also require a 500-foot buffer between stores, which the measure’s proponents say would address concerns people have of stores proliferating and concentrating in specific neighborhoods. They also claim that because of zoning restrictions and other buffer requirements, only about 350 dispensaries would actually be allowed to open within the city.

Council members Paul Koretz and Bill Rosendahl, both outspoken supporters of Proposition D, said the measure strikes a balance between giving people with serious illnesses access to an effective pain reliever — as was intended under a 1996 voter-approved state initiative — while also curbing “illegal” shops selling marijuana for recreational use.

David Welch, a lawyer for Ordinance F proponents, said they have stronger regulations in their initiative that would better protect patients and the community, contending that the opposing measure contains stripped-down requirements that were a “result of lobbying and compromise” between labor unions and the council.

Both measures would would raise the tax for marijuana sales from $50 to $60 per $1,000, which is seen as a possible boon for city coffers. In 2012, the city collected $2.5 million through taxing the gross receipts of marijuana dispensaries, with city officials anticipating an increase with the passage of either Ordinance F or Proposition D.

The measures are also viewed as a way to introduce much-needed regulation of marijuana businesses. The number of collectives in Los Angeles experienced a surge in recent years, climbing to more than 850 dispensaries and prompting some residents to complain that pot shops were growing out of control and contributing to crime.

The council in the last few years has gone back and forth on banning medical marijuana shops, most recently attempting a so-called “gentle ban” that would still allow patients and licensed caregivers, as well as collectives of three or fewer people, to grow their own cannabis for medical use.

The two original petition-driven initiatives were proposed to repeal the gentle ban, but city leaders stepped in with Proposition D, which they touted as a “superior” hybrid, combining Ordinance E’s restriction of dispensaries to the 135 that registered before September 2007 with the tax hike provision
from Ordinance F.

If all three medical marijuana initiatives are approved by voters, the one with the most votes would take effect.

A fourth ballot measure, Proposition C, is a symbolic resolution calling on Los Angeles to support federal legislation that would overturn parts of United States Supreme Court’s rulings in the cases of Buckley v. Valea in 1976 and Citizens United v. Federal Election Commission in 2010.

The rulings have allowed corporations, labor unions and other organizations to be viewed as human beings, giving them wide latitude to participate in political campaigns by contributing unrestricted amounts of money to independent campaign expenditure committees.