SAN FRANCISCO (MarketWatch) -- Billionaire financier George Soros has contributed $1 million to Proposition 19, a ballot measure that would legalize marijuana in California, according to papers filed by the secretary of state's office Tuesday. The contribution, first reported by the Sacramento Bee, comes on the same day that the Wall Street Journal published an opinion piece by Soros in favor of legalizing pot. "The criminalization of marijuana did not prevent marijuana from becoming the most widely used illegal substance in the United States and many other countries. But it did result in extensive costs and negative consequences," Soros wrote.