Voters will determine the future of L.A. medical marijuana shops on the May 21 ballot by choosing between Proposition D, Ordinance E and Ordinance F -- three competing ballot measures that all aim to regulate dispensaries in different ways. 

NOTE: voting "Yes" on all three would be counterproductive. In order to make your vote count, pick the one you most agree with and vote "No" on the two you don't.

While seemingly similar in purpose, the three measures are competing proposals put forward by separate ends of the local cannabis community.  They all look to regulate medical marijuana dispensaries, but in very different ways.

L.A. City Council placed Proposition D on the ballot as a compromise, between Ordinances E and F, which qualified as initiatives by way of signatures. 

Here's what you need to know before you head to the ballot box:

Proposition D:

A "Yes" vote would allow the original 135 dispensaries approved under a 2007 interim control ordinance to remain open, but only if they adhere to the city rules on proximity to schools, churches and neighborhoods.  It also caps the number of operating stores at 135 within the city limit.  

A tax of $60 per $1,000 of marijuana sold would be established under the proposal, increasing the current rate by 20 percent.  

It would also required background checks on all employees, as well as mandated store hours, ordering doors to be closed between the hours of 8 pm and 10 pm.   

Unlike it's opponents, Proposition D allows minors to enter dispensaries as caregivers or patients, but only if accompanied by a parent or legal guardian.

The measure is backed by mayoral candidate Eric Garcetti and L.A. City Council as it was drafted to be a middle ground between the two competing measures.

Ordinance E:

The United Food and Commercial Workers Union was the force behind this initiative making the ballot.  But due to sweeping similarities, Measure E has lost several supporters in recent months to Measure D.

A "Yes" vote on this measure means limiting Medical Marijuana Collectives (MMCs) of six or more patients and caregivers by banning all dispensaries except those registered before 2007.  

Like Measure D, it would also cap the number of stores in the city at 135.  

Ordinance F:

Taking a free market approach, Measure F allows dispensaries to self-regulate themselves through quality control and paying more city taxes.  

Calling itself the "Medical Marijuana Collectives Initiative Ordinance," Measure F made its way to the ballot by submitting roughly 67,000 signatures to officials early this year.

It is the only proposed initiative that would allow medical dispensaries that opened after 2007 to remain in business as long as they meet certain standards. 

Also, it would require shops to test marijuana for pesticides and toxins.  

A 20 percent increase in sales tax would be imposed, similar to Proposition D, but it would also require each dispensary to file an annual CPA-reviewed audit of operations with the city controller's office.

Under Measure F, dispensary access for minors would be strictly prohibited and each dispensary would be required to provide patient parking.  

The measure is sponsored by Angelenos for Safe Access. 

Also See: Why Is Medical Marijuana Regulation In Los Angeles So Confusing?

Reach Reporter Lauren Foliart here.