Uruguay's first round of elections this past weekend may change the law that legalized marijuana late last year.

Tabare Vazquez, a former president and member of the ruling Broad Front leftist coalition, supports the law, but center-right opponent Luis Lacalle Pou does not. He promised to overturn it and only allow personal marijuana cultivation.

Both are the two main presidential contenders

Uruguay is the first country in the world to authorize the production, distribution and sale of marijuana.

Sunday's election is expected to go to a second vote, scheduled for November.

Outgoing President Jose Mujica is backing Vazquez. Last year, Mujica championed marijuana legalization. Yet, support for the law has declined recently.

A July survey by the polling firm Cifra-Gonzalez, Raga & Associates found that more than 60 percent of respondents disapproved of marijuana legalization and thought the law should be repealed as soon as possible, according to the International Business Times.

Details on how the system would work on regulating supply and keeping criminal networks out of the marijuana market have yet to be determined.

The government has delayed its rollout of marijuana sales to early 2015, which would initially make it easier for the next president to stop or stall the experiment if it is not implemented before Mujica leaves office.

Legalization of marijuana would be a step forward in shying away from harsh drug penalties in Uruguay.

Last year, at the announcement of legalization of marijuana, presidential aide Diego Canepa told everyone that the state will control the marijuana market from beginning to end, starting with setting prices.

The law doesn't give foreigners the right to smoke or buy the drug and says consumers, sellers and distributors all have to be licensed by the government, according to CNN reports.

Voters are keeping an eye out for their next leader.