Billionaire and founder of the Open Societies Foundations George Soros on Tuesday wrote an Op-ed in the Wall Street Journal supporting California's Proposition 19, which would legalize marijuana in the state. Soros has reportedly donated millions of dollars to groups supporting the proposition.Among the arguments Soros makes for the legalization of marijuana, he notes that criminalizing the plant did not prevent it from becoming the most widely used illegal substance in the US, and that law enforcement agencies spend billions of dollars "trying to enforce this unenforceable prohibition."RELATED:Soros a secret J Street donor since ’08 Soros to give Human Rights Watch $100m. over 10 yearsWhose Money Is Kosher?Another effect of the plant's criminalization that Soros addressed is the racial inequality that he says is a part of marijuana enforcement, citing that while African Americans are no more likely to use marijuana, they are between five and 10 times more likely to be arrested for possessing it.Addressing the role that marijuana's sources of production and trade, Soros argued that legalizing the drug would undermine Mexican drug cartels and criminal organizations who most benefit from the black-market status of the plant, saying that they would "rapidly lose their competitive advantage if marijuana were a legal commodity," he wrote in the Wall Streeet Journal. Soros notes that three former South American presidents recommended decriminalizing marijuana among their recommendations for the Latin American Commission on Drugs and Democracy.Soros explained that in his view, California's Proposition 19 "is already a winner no matter what happens on election day." By virtue of it being on the ballot, it has raised and legitimized the public discourse on the legalization and use of marijuana, "in ways I could not have imagined a year ago."Soros, a Hungarian-American Jew who was ranked as the 6th most wealthy Jew last month, is the founding chairman of Soros Fund Management and heads the Open Society Institute, a grant-making foundation. An effective liberal activist, he is credited with a significant role in his native Hungary’s peaceful transition from communism to capitalism in the 1980s, and in the Georgian Rose Revolution of 2003, and he was a passionate critic of president George W. Bush.