Chicago Mayor Rahm Emanuel said he would back a proposal that would decriminalize possessing small amounts of marijuana, the latest major U.S. political figure to support diminished penalties for the drug's use. Under the proposed ordinance, to be voted on by the city council later this month, police officers in the nation's third-largest city would be able to issue a written violation for possession of 15 grams or less. This is a modified version of an ordinance proposed last fall by a group of Chicago aldermen, who said the measure would help raise revenue for the city, save money and free up police to pursue more serious crimes.